Patent Application
20230030158
The present invention relates to an optical communication apparatus, an optical communication system, and an optical communication method.
The number of users who use high-speed Internet via fiber-to-the-home (FTTH) and mobile services has been increasing. High-speed Internet has become an indispensable part of people's lives. On the other hand, in a backbone network that provides FTTH and mobile services, networks are separately constructed for services. This is inefficient in terms of operation. Thus, an access network that accommodates a plurality of services with one device has been proposed (see, for example, NPL 1). Further, to realize an access network capable of accommodating multiple services, a passive optical network (PON) such as a wavelength division multiplexing PON (WDM-PON) that uses a plurality of wavelengths or a time division multiplexing PON (TDM-PON) have been standardized by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) (see, for example, NPL 2).
On the other hand, in existing optical access systems, communications between terminal devices on the subscriber side and devices on the stations are connected to an upper level core network. The terminal devices on the subscriber side are, for example, optical network units (ONUS). Connections to the core network are made via a terminal device in an apparatus on the station side. The terminal device is, for example, an optical line terminal (OLT). In optical access to connect to the core network by packet switching, a process of adding or deleting user information or destination information, a routing process, and the like are performed on signals, and when user information or destination information is added or deleted, an optical signal may be temporarily converted into an electrical signal. This causes some delay in communication. Also, when the amount of data increases, signals may be stored in buffers and priority control or the like may be performed. This further increases the delay. As the delay increases, the quality of optical service drops significantly. Thus, it is important to reduce delay as much as possible.
To improve the quality of optical services and provide various services via optical access networks, it is necessary to reduce the delay that occurs. The delay can be greatly reduced by using an optical switch or the like that can perform processing such as routing without converting an optical signal into an electrical signal.
NPL 1: Shunji Kimura, “Elastic Lambda Aggregation Network (DAN)—Proposal for Future Optical Access Network—,” 2013 18th OptoElectronics and Communications Conference held jointly with 2013 International Conference on Photonics in Switching (OECC/PS), WP4-4, 2013
However, in routing using an optical switch, it is necessary to set a path of an optical signal according to the destination of a subscriber terminal and further make a setting (of a wavelength or the like) on the transceiver of the subscriber terminal.
In view of the above circumstances, it is an object of the present invention to provide an optical communication apparatus, an optical communication system, and an optical communication method, whereby a setting that allows the use of a path corresponding to a destination can be made on a subscriber terminal and an optical signal transmitted from the subscriber terminal can be relayed according to the destination.
An aspect of the present invention is an optical communication apparatus including an optical switch that is connected to a plurality of transmission lines and that outputs an optical signal input from one of the plurality of transmission lines to another of the plurality of transmission lines, a wavelength management control unit that assigns a wavelength to a subscriber terminal according to a communication destination, and an optical switch control unit that controls the optical switch such that the optical switch outputs an optical signal transmitted from the subscriber terminal to which a wavelength is assigned to a transmission line according to a forwarding destination on a path to the communication destination.
An aspect of the present invention is an optical communication apparatus including an optical switch that is connected to a plurality of transmission lines and that outputs an optical signal input from one of the plurality of transmission lines to another of the plurality of transmission lines, a wavelength management control unit that dynamically assigns a wavelength to a subscriber terminal according to a communication destination, and an optical switch control unit configured to control the optical switch such that the optical switch outputs an optical signal input from a transmission line of the plurality of transmission lines to a transmission line of the plurality of transmission lines according to a communication destination identified by a combination of the subscriber terminal that transmits the optical signal input and a wavelength of the optical signal input.
An aspect of the present invention is an optical communication system including a plurality of subscriber terminals and the optical communication apparatus described above, in which one of the plurality of subscriber terminals includes one or both of an optical transmission unit that transmits an optical signal of a wavelength assigned by the optical communication apparatus and an optical reception unit that receives an optical signal of a wavelength assigned by the optical communication apparatus.
An aspect of the present invention is an optical communication method including outputting, by an optical switch connected to a plurality of transmission lines, an optical signal input from one of the plurality of transmission lines to another of the plurality of transmission lines, assigning, by a wavelength management control unit, a wavelength to a subscriber terminal according to a communication destination, and controlling, by an optical switch control unit, the optical switch such that the optical switch outputs an optical signal transmitted from the subscriber terminal to which a wavelength is assigned to a transmission line according to a forwarding destination on a path to the communication destination.
An aspect of the present invention is an optical communication method including outputting, by an optical switch connected to a plurality of transmission lines, an optical signal input from one of the plurality of transmission lines to another of the plurality of transmission lines, dynamically assigning, by a wavelength management control unit, a wavelength to a subscriber terminal according to a communication destination, and controlling, by an optical switch control unit, the optical switch such that the optical switch outputs an optical signal input from a transmission line of the plurality of transmission lines in the outputting to a transmission line of the plurality of transmission lines according to a communication destination identified by a combination of the subscriber terminal that transmits the optical signal input and a wavelength of the optical signal input.
According to the present invention, a setting that allows the use of a path corresponding to a destination can be made on a subscriber terminal and an optical signal transmitted from the subscriber terminal can be relayed according to the destination.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same parts are denoted by the same reference signs and description thereof is omitted. In the present embodiment, in response to a connection request from each subscriber terminal, a wavelength to be used by the subscriber terminal is assigned in cooperation with a wavelength controller, an optical switch controller, and a management database that manages connection information of all subscribers. Here, a device for controlling subscriber terminals is used to transmit setting information such as the wavelength to be used to each subscriber terminal. The control device and subscriber terminals communicate, for example, using control signals that are slower than main signals, which are optical signals between subscriber terminals, and that can be superimposed on main signals. This makes it possible to perform setting change or monitoring without affecting main signals. Further, in the present embodiment, an optical switch is controlled such that an optical signal transmitted from a subscriber terminal to which a wavelength has been assigned is output to a transmission line corresponding to a forwarding destination on a path to a communication destination. In the present embodiment, for example, in the case where a wavelength is used as destination information, the optical switch is controlled to perform routing using a wavelength as destination information. Thereby, in the present embodiment, a setting that allows the use of a path corresponding to a destination is made on a subscriber terminal and an optical signal transmitted from the subscriber terminal is relayed according to the destination using the path. Delays caused by a process of adding or deleting user information or destination information and a routing process when packets are transferred can also be reduced.
A subscriber terminal, an input port, a combination of a subscriber terminal and a wavelength, a combination of an input port and a wavelength, and a combination of an input port, a subscriber terminal, and a wavelength may also be used as destination information. The following embodiments will be described mainly with reference to the case where a combination of a subscriber terminal and a wavelength is used as destination information.
The control unit 20 includes an optical transceiver 21. The optical transceiver 21 is an example of a configuration of an optical transmission unit and an optical reception unit in the control unit 20. The optical transceiver 21 includes an optical transmitter (Tx) 22 and an optical receiver (Rx) 23. The optical transceiver 21 is a wavelength-variable optical transceiver. The control unit 20 stores a wavelength management table. The wavelength management table is data indicating wavelengths assigned to each of subscriber terminals 40. The control unit 20 uses the AMCC function to assign each subscriber terminal 40 a wavelength to be used by the subscriber terminal 40 for communication. In the following, communications between each subscriber terminal 40 and the control unit 20 will be exemplified, but not limited, by the AMCC function.
To assign a wavelength corresponding to the destination to the subscriber terminal 40, first, the optical transceiver 41 of the subscriber terminal 40 and the optical transceiver 21 of the control unit 20 communicate with each other using AMCC. The control unit 20 refers to the wavelength table and selects a wavelength to be assigned to the subscriber terminal 40 according to the destination. In an example, the control unit 20 selects a wavelength from available wavelengths that are not used for other paths in links that multiplex wavelengths on the paths. The control unit 20 may also assign an individual wavelength to each subscriber terminal 40. The control unit 20 sets the selected wavelength in the subscriber terminal 40 by a control signal using AMCC. After that, the control unit 20 switches the optical switch 10 such that it performs routing according to the destination of an optical signal transmitted from the subscriber terminal 40. For example, when a wavelength is used as destination information, the control unit 20 switches the optical switch such that it performs routing to a destination indicated by the wavelength. In this way, the control unit 20 connects opposing subscriber terminals 40.
An optical switch 10 is provided, for example, in an optical gateway (GW). Examples of an optical switch 10 provided in an optical gateway will be described with reference to
Each port 11-1 is connected to a subscriber terminal 40 via a transmission line 50-1. Each port 11-2 is connected to a subscriber terminal 40 via a transmission line 50-2. Each subscriber terminal 40 is, for example, an ONU. Each transmission line 50-2 may be connected to an optical communication network 30 which is an upper level network. In this case, the direction toward the subscriber terminal 40 connected via a transmission line 50-1 is downstream and the direction toward the upper level network connected via a transmission line 50-2 is upstream. Each transmission line 50-2 may be provided with another optical communication apparatus such as another optical switch 10.
The ports 11-1-1, 11-1-2, 11-1-3, . . . are connected to subscriber terminals 40a-1, 40a-2, 40a-3, . . . , which are subscriber terminals 40 of a link end A, via transmission lines 50-1. The subscriber terminals 40a-1, 40a-2, 40a-3, . . . will be collectively, or when any of them is not specified, referred to as subscriber terminals 40a. One of the ports 11-2 (the port 11-2-1 in
The optical switch 10a is connected to the control unit 20. The control unit 20 includes the wavelength management control unit 25 and an optical switch control unit 26. The wavelength management control unit 25 performs a wavelength assignment process of receiving a request for wavelength assignment from a subscriber terminal 40 by an optical signal, assigning a wavelength corresponding to a communication destination to the subscriber terminal 40 that has transmitted the request, and notifying the subscriber terminal 40 of the assigned wavelength by an optical signal. For example, the wavelength management control unit 25 may dynamically assign a wavelength corresponding to the communication destination to the subscriber terminal 40 that has transmitted the request. It is preferable that a management control signal superimposition method that does not rely on the communication protocol of optical signals (main signals) between subscriber terminals 40 be used for optical signals transmitted and received between the wavelength management control unit 25 and subscriber terminals 40. For example, protocol-free AMCC is used for optical signals transmitted and received between the wavelength management control unit 25 and subscriber terminals 40.
The optical switch control unit 26 controls the optical switch 10a such that an optical signal is transmitted and received between the subscriber terminal 40 and the wavelength management control unit 25 while the wavelength assignment process is being performed. After the wavelength assignment process, the optical switch control unit 26 controls the optical switch 10a such that it outputs an optical signal input from a transmission line 50 to a transmission line 50-2 corresponding to a communication destination identified by a combination of the subscriber terminal 40 that has transmitted the input optical signal and the wavelength of the input optical signal.
Each transmission line 50-2 is provided with a monitoring circuit 60. Only one monitoring circuit 60 is illustrated in
When a subscriber terminal 40 is connected to a transmission line 50-2, the control unit 20 may be connected to a port 11-1. Alternatively, when a subscriber terminal 40 is connected to a transmission line 50-2, the subscriber terminal 40 connected to the transmission line 50-2 may be connected to the control unit 20 via a return transmission line 73. The return transmission line 73 is an optical fiber through which an optical signal output from a port 11-1-p1 is input to another port 11-1-p2 (where pl and p2 are integers of 1 or more and P or less). In this case, an optical signal transmitted from a subscriber terminal 40b or 40c is input to the optical switch 10a via a transmission line 50-2. The optical switch 10a outputs the optical signal input from the transmission line 50-2 to the port 11-1-p1 and receives the optical signal transmitted through the return transmission line 73 from the port 11-1-p2. The optical switch 10a outputs the optical signal input from the port 11-1-p2 to the control unit 20 from the port 11-2-1. In this way, the subscriber terminal 40b or 40c is connected to the control unit 20.
The wavelength management control unit 25 may perform a wavelength change process of instructing a subscriber terminal 40, on which a wavelength assignment process has been performed, to change the wavelength. For example, the wavelength management control unit 25 identifies a subscriber terminal 40 whose wavelength is to be changed based on monitoring information output from a monitoring circuit 60 and performs a wavelength change process on the identified subscriber terminal 40. The optical switch control unit 26 controls the optical switch 10a such that an optical signal is transmitted and received between the subscriber terminal 40 and the wavelength management control unit 25 during the wavelength change process. When an optical signal of the changed wavelength has been input from the subscriber terminal 40 after the wavelength change process, the optical switch control unit 26 controls the optical switch 10a such that it outputs the input optical signal to a transmission line 50-2 corresponding to the communication destination. For example, the optical switch control unit 26 controls the optical switch 10a such that it receives an optical signal of the changed wavelength input from the subscriber terminal 40 after the wavelength change process and outputs the input optical signal to a transmission line 50-2 corresponding to the communication destination for which a combination of the transmission source subscriber terminal 40 and the wavelength before the change has been used. Alternatively, the optical switch control unit 26 controls the optical switch 10a such that it outputs the optical signal transmitted from the transmission source subscriber terminal 40 using the changed wavelength to a transmission line 50-2 different from that before wavelength change. In this case, communication destination subscriber terminals 40 before and after the wavelength change process are different. The wavelength management control unit 25 may receive a wavelength change request from a subscriber terminal 40 during or after completion of communication and perform a wavelength change process on the requesting subscriber terminal 40. Through the wavelength change process, both the wavelength used for transmission and the wavelength used for reception by the subscriber terminal 40 may be changed or either of them may be changed.
When a port which is the output destination of the optical signal is set by a combination of the transmission source subscriber terminal 40 and the wavelength, the destination for the direction from a port 11-1 to a port 11-2 to which the return transmission line 51 is connected and the destination for the direction from a port 11-2 to which the return transmission line 51 is connected to a port 11-1 may differ.
The optical switch 10c may receive optical signals of a plurality of wavelengths from a port 11-1. In this case, the optical switch 10c distributes the optical signals of the plurality of wavelengths received from the port 11-1 through the distribution unit 58 and outputs the distributed optical signals to subscriber terminals 40 connected to ports 11-2 or transmission lines connected to another link end. Each of the subscriber terminals 40 connected to the ports 11-2 selects and receives an optical signal of a predetermined wavelength from the optical signals of the plurality of wavelengths. The transmission lines connected to the other link end may each transmit the same optical signals as those of the plurality of wavelengths or may each transmit an optical signal of a wavelength selected by a WDM device illustrated in
The optical switch 10d may receive optical signals of a plurality of wavelengths from a port 11-2. In this case, the optical switch 10c distributes the optical signals of the plurality of wavelengths received from the port 11-2 by using the distribution unit 59 and outputs the distributed optical signals to subscriber terminals 40 connected to ports 11-1. Each of the subscriber terminals 40 connected to the ports 11-1 selects and receives an optical signal of a predetermined wavelength from the received optical signals of the plurality of wavelengths.
Each multiplexed communication transmission line 90 is provided with a monitoring circuit 65. The monitoring circuit 65 includes a power splitter 66 and WDM devices 67 and 68. The power splitter 66 splits off an optical signal transmitted through the multiplexed communication transmission line 90. The WDM device 67 demultiplexes an upstream optical signal split off by the power splitter 66. The WDM device 68 demultiplexes a downstream optical signal split off by the power splitter 66. The monitoring circuit 65 monitors optical signals demultiplexed by the WDM devices 67 and 68. The monitoring circuit 65 generates monitoring information based on the monitoring result and outputs the generated monitoring information. The monitoring information is information indicating the monitoring result or information obtained from the monitoring result. For example, upon detecting an abnormality in the communication status between subscriber terminals 40 by monitoring the optical signals, the monitoring circuit 65 outputs monitoring information in which information indicating the occurrence of an abnormality in the communication status and information identifying a subscriber terminal 40 in which the abnormality in the communication status has occurred are set. The output destination of the monitoring information is, for example, the control unit 20.
Each monitoring circuit 65 may be provided with power splitters 69 in transmission lines between ports 11-2 and the WDM device 80. Each power splitter 69 splits off an optical signal transmitted through a transmission line between a port 11-2 and the WDM device 80 and outputs the split optical signal to the control unit 20.
The wavelength management control unit 25 may perform a wavelength change process of instructing a subscriber terminal 40, on which a wavelength assignment process has been performed, to change the wavelength. For example, the wavelength management control unit 25 identifies a subscriber terminal 40 whose wavelength is to be changed based on monitoring information output from a monitoring circuit 65 and performs a wavelength change process on the identified subscriber terminal 40. The optical switch control unit 26 controls the optical switch 10e such that an optical signal is transmitted and received between the subscriber terminal 40 and the wavelength management control unit 25 during the wavelength change process. When an optical signal of the changed wavelength has been input from the subscriber terminal 40 after the wavelength change process, the optical switch control unit 26 controls the optical switch 10e such that it outputs the input optical signal to a port 11-2 corresponding to the communication destination. The wavelength management control unit 25 may receive a wavelength change request from a subscriber terminal 40 during or after completion of communication and perform a wavelength change process on the requesting subscriber terminal 40.
An example of wavelength change in the optical switch 10e will be described with reference to
In
The optical switch control unit 26 may also control the optical switch 10e such that, after the wavelength change process, it outputs an optical signal, which has been transmitted from the transmission source subscriber terminal 40 using the changed wavelength, to a WDM device 80 different from that before wavelength change.
The wavelength management control unit 25 may operate as follows when the subscriber terminal 40a-2 uses a wavelength as destination information and does not change the wavelength used for reception. The following does not apply when a wavelength is not used as destination information.
(1) The wavelength management control unit 25 releases a transmission wavelength that has been used by the subscriber terminal 40 of the link end B which is the communication destination before wavelength switching. Releasing the transmission wavelength resets the path from the subscriber terminal 40a-2, which uses the wavelength as destination information, to the subscriber terminal 40 of the link end B. After that, the wavelength management control unit 25 reassigns the wavelength, which has become an available wavelength due to the release, for receiving a signal addressed to the subscriber terminal 40a-2 from a subscriber terminal 40 of the link end C which is a new communication destination. This is performed when wavelengths used for subscriber terminals 40 are unique and no wavelengths other than idle wavelengths are assigned.
(2) When the communication destinations before and after wavelength change of the subscriber terminal 40a-2 are subscriber terminals 40 connected via different multiplexed communication transmission lines 90, the same wavelength as that used before wavelength change can be reused. However, for example, when transmission is made via a different transmission line or when input or output is made through a different input or output port of the optical switch while a wavelength is used as destination information, the path is treated as a different path, even with the same wavelength. To enable such reuse, for example, an “input transmission line,” an “output transmission line,” or a “combination of all transmission lines constituting the path” is added to arguments which are conditions for determining the output destination of the optical signal. The output destination is determined, for example, by a combination of a transmission line or a port to which an optical signal has been input and the wavelength of the optical signal or a combination of a transmission line or a port to which an optical signal has been input, a subscriber terminal 40 that has transmitted the optical signal, and the wavelength of the optical signal.
While a wavelength change process performed when a subscriber terminal 40 has requested a wavelength change has been described above, the same applies to a wavelength change process performed based on monitoring information.
An optical switch that performs WDM transmission and multicast will be described with reference to
Each subscriber terminal 40 may output a WDM signal. For example, a subscriber terminal 40 outputs a WDM signal into which an optical signal of a wavelength λ1 and an optical signal of a wavelength λ2 are multiplexed. Further, a plurality of transmission lines between a WDM device 80b and the optical switch 10f transmit and receive optical signals of wavelengths λ1, λ2, . . . in order from the top. Similarly, a plurality of transmission lines between a WDM device 80c and the optical switch 10f transmit and receive optical signals of wavelengths λ1, λ2, . . . in order from the top.
The optical switch 10f distributes a WDM signal of wavelengths λ1 and λ2 input from a port 11-1 connected to the subscriber terminal 40 through the distribution unit 58. The optical switch 10f outputs a distributed WDM signal to a port 11-2 corresponding to the wavelength λ1 among ports 11-2 connected to the WDM device 80b. Further, the optical switch 10f outputs another distributed WDM signal to a port 11-2 corresponding to the wavelength λ2 among ports 11-2 connected to the WDM device 80c. The WDM device 80b filters the WDM signal input from the port corresponding to the wavelength λ1 to pass an optical signal of the wavelength λ1 while blocking the wavelength λ2 and outputs the passed optical signal to a multiplexed communication transmission line 90. The WDM device 80c filters the WDM signal input from the port corresponding to the wavelength λ2 to pass an optical signal of the wavelength λ2 while blocking the wavelength λ1 and outputs the passed optical signal to a multiplexed communication transmission line 90.
The optical switch 10f outputs optical signals distributed by the power splitter 71 to a port 11-2 corresponding to the wavelength λ1 and a port 11-2 corresponding to the wavelength λ2 among ports 11-2 connected to the WDM device 80b. Further, the optical switch 10f outputs optical signals distributed by the power splitter 71 to a port 11-2 corresponding to the wavelength λ1 and a port 11-2 corresponding to the wavelength λ2 among ports 11-2 connected to the WDM device 80c. The WDM device 80b filters the optical signal input from the port corresponding to the wavelength λ1 to pass an optical signal of the wavelength λ1 and outputs the passed optical signal to a multiplexed communication transmission line 90 and filters the optical signal input from the port corresponding to the wavelength λ2 to pass an optical signal of the wavelength λ2 and outputs the passed optical signal to the multiplexed communication transmission line 90. Similarly, the WDM device 80c filters the optical signal input from the port corresponding to the wavelength λ1 to pass an optical signal of the wavelength and outputs the passed optical signal to a multiplexed communication transmission line 90 and filters the optical signal input from the port corresponding to the wavelength λ2 to pass an optical signal of the wavelength λ2 and outputs the passed optical signal to the multiplexed communication transmission line 90.
Under the control of the optical switch control unit 26, the optical switch 10h outputs an optical signal input from a subscriber terminal 40 from a port 11-2 or the port 12-1 according to a combination of the subscriber terminal 40 which is the transmission source of the optical signal or a port 11-1 from which the optical signal has been input and the wavelength. Under the control of the optical switch control unit 26, the optical switch 10h outputs an optical signal output destination input from a port 11-2 from a port 11-1 or the port 12-1 according to a combination of the port 11-2 from which the optical signal has been input and the wavelength.
The optical switch 10h outputs an optical signal from the port 12-1 to drop the optical signal to the electrical processing unit 84. The electrical processing unit 84 electrically terminates the dropped optical signal and applies various electrical processing such as error correction and line concentration and then converts the processed signal into an optical signal and inputs the optical signal to the port 12-2 of the optical switch 10h. The optical switch 10h outputs the optical signal input from the electrical processing unit 84 from a port 11-1 or a port 11-2 corresponding to a destination identified by the combination of the port 12-2 and the wavelength. In this way, the electrical processing unit 84 performs O-E(electrical processing addition)-O conversion (where O refers to optical and E refers to electrical). The electrical processing unit 84 may simply perform O-E-O conversion without performing electrical processing for adding a function. Upon O-E-O conversion or the like, the electrical processing unit 84 performs 3R reproduction (Re-amplification, Re-timing (timing reproduction), and Re-shaping (waveform shaping)) or uses threshold effects through 0/1 reversal, such that it is possible to reduce deterioration of the optical waveform due to transmission. The wavelength of an optical signal that is to be converted into an electrical signal and the wavelength of an optical signal into which the electrical signal has been converted may be the same or different.
When a port which is the output destination of the optical switch is determined by a combination of a subscriber terminal that has transmitted the optical signal and the wavelength, that is, when the wavelength is used as destination information, the destination for the direction from a port 11-1 to a port 11-2 and the destination for the direction from a port 11-2 to a port 11-1 may differ even with the same wavelength, for passing through the electrical processing unit 84.
The electrical processing unit 84 includes an optical to electrical (0/E) conversion unit 85, a processing execution unit 86, an electrical to optical (E/O) conversion unit 87, and a storage unit 88. The O/E conversion unit 85 converts an optical signal input from the optical switch 10h into an electrical signal. The processing execution unit 86 includes a processor 861 and an accelerator 862. The processor 861 is a general-purpose processor such as a central processing unit (CPU). The accelerator 862 is, for example, a processor such as a graphics processing unit (GPU). Each of the processor 861 and the accelerator 862 reads a program from the storage unit 88 and executes it to perform electrical signal processing on the electrical signal produced through conversion of the O/E conversion unit 85. The processing execution unit 86 may perform electrical signal processing of a plurality of functions. Examples of electrical signal processing include digital signal processing (DSP) for long distance/high-speed access, mobile fronthaul processing, and error correction. The E/O conversion unit 87 converts the electrical signal into an optical signal of a wavelength indicated by the optical switch control unit 26 and outputs the optical signal to the optical switch 10h. The storage unit 88 stores a program for the processor 861 and the accelerator 862 to execute the functions of electrical signal processing.
By implementing the processing execution unit 86 with a device architecture based on a general-purpose processor, it is possible to add and change electrical signal processing while enabling replacement with various functions other than the transmission function. Also, a dedicated large-scale integration (LSI) for long-distance/high-speed access becomes unnecessary because the processing execution unit 86 performs DSP for long-distance/high-speed access. Thus, flexible function deployment according to needs is realized.
The optical switch 10h may be connected to a plurality of electrical processing units 84. In this case, the optical switch 10h has a plurality of pairs of ports 12-1 and 12-2 connected to the plurality of the electrical processing units 84. Each of the electrical processing units 84 may perform different electrical signal processing or some or all of them may perform the same electrical processing.
The processing execution unit 86 and the storage unit 88 may be realized using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA).
The operation of the optical switch 10h will be described with reference to
Also, the optical switch 10h receives a downstream optical signal addressed to the subscriber terminal 40-1 transmitted through the multiplexed communication transmission line 90. The optical switch 10h outputs the received downstream optical signal to the electrical processing unit 84 from the port 12-1 according to a combination of a port 51-2 from which the optical signal has been input and the wavelength. The O/E conversion unit 85 of the electrical processing unit 84 converts the input optical signal into an electrical signal and the processing execution unit 86 performs DSP processing for long-distance/high-speed access on the converted electrical signal. The E/O conversion unit 87 converts the DSP-processed electrical signal into an optical signal and outputs it to the optical switch 10h. The wavelength of the optical signal after conversion may be the same as or different from the wavelength when it is input to the electrical processing unit 84. The optical switch 10h outputs the optical signal input from the electrical processing unit 84 to a port 11-1 connected to the subscriber terminal 40-1.
Optical signals transmitted and received by the subscriber terminals 40-2 are subjected to the same processing as that performed on optical signals transmitted and received by the subscriber terminal 40-1 described above. However, the processing execution unit 86 performs mobile fronthaul processing on optical signals transmitted and received by the subscriber terminals 40-2. The processing execution unit 86 determines signal processing to be performed on the electrical signal based on arbitrary information included in the electrical signal.
On the other hand, the optical switch 10h outputs an upstream optical signal input from the subscriber terminal 40-3 to the multiplexed communication transmission line 90 from a port 11-2. The optical switch 10h receives a downstream optical signal addressed to the subscriber terminal 40-3 transmitted through the multiplexed communication transmission line 90 and outputs the received optical signal to a port 11-1 connected to the subscriber terminal 40-3 according to a combination of the port 11-2 from which the optical signal has been received and the wavelength.
Subsequently, access topologies to an optical switch will be described with reference to
A power splitter 56 is provided on a transmission line 50-1-p. Np subscriber terminals 40-p (where Np is an integer of 2 or more) are connected to the power splitter 56 in a star configuration. The Np subscriber terminals 40-p will be referred to as subscriber terminals 40-p-1 to 40-p-Np and a transmission line 50-1-p between a subscriber terminal 40-p-np (where np is an integer of 1 or more and Np or less) and the power splitter 56 will be referred to as a transmission line 50-1-p-np. The subscriber terminals 40-p-1 to 40-p-Np use the same wavelength by time division multiplexing. The wavelength used for upstream optical signals and the wavelength used for downstream optical signals are different.
The optical switch 1001 receives downstream optical signals of a wavelength addressed to the subscriber terminals 40-p-1 to 40-p-Np, which have been time-division-multiplexed, from a port 11-2-q. The optical switch 1001 outputs the received downstream optical signals from a port 11-1-p which is an output destination corresponding to a combination of the port 11-2-q and the wavelength The power splitter 56 receives the time-division-multiplexed downstream optical signal from the transmission line 50-1-p and splits and outputs the received optical signal to the transmission lines 50-1-p-1 to 50-1-p-Np. Each of the subscriber terminals 40-p-1 to 40-p-Np receives the time-division-multiplexed optical signal and selects a downstream optical signal addressed to the subscriber terminal from the received optical signal.
The subscriber terminals 40-p-1 to 40-p-Np transmit time-division-multiplexed upstream optical signals of the same wavelength λ2 by time-division multiple access (TDMA). The power splitter 56 receives upstream optical signals of the wavelength λ2 from the transmission lines 50-1-p-1 to 50-1-p-Np and time-division-multiplexes the received optical signals and outputs the time-division-multiplexed signal to the transmission line 50-1-p. The optical switch 1001 outputs the time-division-multiplexed upstream optical signal from a port 11-2-q corresponding to a combination of the port 11-1-p and the wavelength λ2.
The PDS access topology can be applied to any one or more of the transmission lines 50-1-1 to 50-1-P.
In
The optical switch 1002 receives a downstream optical signal of a wavelength λ1(q+n) addressed to a subscriber terminal 40-(p+n) from a port 11-2-(q+n) (where q is an integer of 1 or more and n is an integer of 0 or more and N or less).
The WDM device 81 multiplexes downstream optical signals of wavelengths iii to λ1N output from the ports 11-1-p to 11-1-(p+N) and outputs the multiplexed optical signal to the multiplexed communication transmission line 91. The power splitter 56 receives the wavelength-multiplexed downstream optical signal from the multiplexed communication transmission line 91, splits the received downstream optical signal into the same signals, and outputs them to the transmission lines 92 between the power splitter 56 and the subscriber terminals 40-p to 40-(p+N). Each of the subscriber terminals 40-p to 40-(p+N) receives the wavelength-multiplexed downstream optical signal and selects a downstream optical signal of a wavelength to be used by the subscriber terminal from the received optical signal.
Each subscriber terminal 40-(p+n) transmits an upstream optical signal of a wavelength λ2(1+n). The power splitter 56 receives upstream optical signals from the subscriber terminals 40-p to 40-(p+N) via the transmission lines 92, wavelength-multiplexes the received upstream optical signals of wavelengths λ21 to λ2(1+n), and outputs the wavelength-multiplexed optical signal to the multiplexed communication transmission line 91. The WDM device 81 receives the wavelength-multiplexed upstream optical signal from the multiplexed communication transmission line 91 and wavelength-demultiplexes the wavelength-multiplexed upstream optical signal. The WDM device 81 inputs the upstream optical signals of wavelengths λ2(1+n) to the ports 11-1-(p+n). The optical switch 1002 outputs the upstream optical signal of each wavelength) λ2(1+n) from a port 11-2-(q+n) which is an output destination corresponding to a combination of the input port 11-1-(p+n) and the wavelength λ2(1+n). In this way, the optical switch 1002 receives the upstream optical signal of the wavelength λ21 transmitted by the subscriber terminal 40-p from the port 11-1-p and outputs it from the port 11-2-1. The optical switch 1002 also receives the upstream optical signal of the wavelength λ22 transmitted by the subscriber terminal 40-(p+1) from the port 11-1-(p+1) and outputs it from the port 11-2-2. The WDM device may also be disposed subsequent to the optical switch as illustrated in
The WDM device 97 receives a downstream optical signal addressed to a subscriber terminal 40-p-n of a wavelength λ1n transmitted from a link end #n from a transmission line 50-2-q-n. The WDM device 97 inputs a wavelength-multiplexed signal, into which downstream optical signals of λ11 to λ1N received from the link ends #1 to #N are multiplexed, to the optical switch 1003. The optical switch 1003 outputs the wavelength-multiplexed downstream signal input from the port 11-2-q from the output destination port 11-1-p. The power splitter 56 splits the wavelength-multiplexed signal input from the transmission line 50-1-p and outputs the split signals to the transmission lines 50-1-p-1 to 50-1-p-N. Each of the subscriber terminals 40-p-1 to 40-p-N receives the wavelength-multiplexed signal and selects a downstream optical signal addressed to the subscriber terminal from the received optical signal. In this way, the subscriber terminal 40-p-n receives an optical signal of the wavelength λ1n from the link end #n.
Each subscriber terminal 40-p-n transmits an upstream optical signal of a wavelength λ2n. The power splitter 56 receives upstream optical signals of wavelengths λ21 to λ2N from the subscriber terminals 40-p-1 to 40-p-N via the transmission lines 50-1-p-1 to 50-1-p-N. The power splitter 56 outputs a wavelength-multiplexed signal, into which the upstream optical signals of the wavelengths λ21 to λ2N are wavelength-multiplexed, to the transmission line 50-1-p. The optical switch 1003 receives the wavelength-multiplexed signal, into which the upstream optical signals of the wavelengths λ21 to λ2N are wavelength-multiplexed, from the port 11-1-p. The optical switch 1003 outputs the wavelength-multiplexed upstream signal to the transmission line 50-2-q from the output destination port 11-2-q. The WDM device 97 receives the wavelength-multiplexed upstream optical signal from the transmission line 50-2-q and wavelength-demultiplexer the wavelength-multiplexed upstream optical signal. The WDM device 97 outputs the upstream optical signal of the wavelength λ2n to a transmission line 50-2-n connected to the link end #n. In this way, the optical signal of the wavelength λ2n transmitted by the subscriber terminal 40-p-n is transmitted to the link end #n.
The subscriber terminals 40-p-1 to 40-p-Np use the same wavelength by time division multiplexing. The wavelength used for upstream optical signals and the wavelength used for downstream optical signals are different. A transmission line 50-2-1 connected to a link end #1 transmits a time-division-multiplexed downstream optical signal of a wavelength addressed to each of the subscriber terminals 40-p-1 to 40-p-Np. The optical switch 1004 receives the time-division-multiplexed downstream optical signal of the wavelength transmitted through the transmission line 50-2-1 from the port 11-2-1. The optical switch 1004 routes the received downstream optical signal to a port 11-1-p which is an output destination corresponding to a combination of the port 11-2-1 (or the link end #1) and the wavelength The optical switch 1004 outputs the time-division-multiplexed downstream optical signal of the wavelength i to the transmission line 50-1-p from the port 11-1-p. Each power splitter 55-n splits off the time-division-multiplexed downstream optical signal from the transmission line 50-1-p and outputs the split downstream optical signal to the subscriber terminal 40-p-n. Each of the subscriber terminals 40-p-1 to 40-p-Np receives the time-division-multiplexed downstream optical signal and selects a downstream optical signal addressed to the subscriber terminal from the received downstream optical signal.
The subscriber terminals 40-p-1 to 40-p-Np transmit time-division-multiplexed upstream optical signals of the same wavelength λ2 by time-division multiple access (TDMA). Each power splitter 55-n time-division-multiplexes an upstream optical signal of the wavelength λ2 input from the subscriber terminal 40-p-n with an upstream optical signal transmitted through the transmission line 50-1-p. The optical switch 1004 receives the time-division-multiplexed upstream optical signal from the port 11-1-p, routes it to the port 11-2-1 which is an output destination corresponding to a combination of the port 11-1-p and the wavelength λ2, and outputs it to the transmission line 50-2-1 connected to the link end #1.
The bus access topology can be applied to any one or more of the transmission lines 50-1-1 to 50-1-P.
Similar to the optical switch 1002 illustrated in
The WDM device 81 multiplexes downstream optical signals of wavelengths λ11 to λ1N output from the ports 11-1-p to 11-1-(p+N) and outputs the multiplexed optical signal to the multiplexed communication transmission line 91. The power splitter 55-(p +n) splits off the wavelength-multiplexed downstream optical signal from the multiplexed communication transmission line 91 and outputs the split downstream optical signal to the subscriber terminal 40-(p+n). Each of the subscriber terminals 40-p to 40-(p+N) receives the wavelength-multiplexed downstream optical signal and selects a downstream optical signal addressed to the subscriber terminal from the received downstream optical signal.
The subscriber terminal 40-(p+n) transmits an upstream optical signal of a wavelength λ2(1+n). Each power splitter 55-(p+n) multiplexes an upstream optical signal of the wavelength λ2(1+n) input from the subscriber terminal 40-(p+n) with an upstream optical signal of wavelengths) λ2(2+n) to λ2N transmitted through the multiplexed communication transmission line 91. The WDM device 81 receives the wavelength-multiplexed upstream optical signal from the multiplexed communication transmission line 91 and demultiplexer it into upstream optical signals of the wavelengths λ21 to λ2N. The WDM device 81 inputs the upstream optical signals of wavelengths λ2(1+n) to the ports 11-1-(p+n). Similar to the optical switch 1002 illustrated in
The WDM device 97 receives a downstream optical signal addressed to a subscriber terminal 40-p-n of a wavelength λ1n transmitted from a link end #n from a transmission line 50-2-q-n. The WDM device 97 inputs a wavelength-multiplexed signal, into which downstream optical signals of wavelengths λ11 to λ1N received from the link ends #1 to #N are multiplexed, to the optical switch 1006. The optical switch 1006 outputs the wavelength-multiplexed downstream signal input from the port 11-2-q from the output destination port 11-1-p. The power splitter 55-n splits off the wavelength-multiplexed downstream signal from the transmission line 50-1-p and outputs the split wavelength-multiplexed downstream signal to the subscriber terminal 40-p-n. Each of the subscriber terminals 40-p-1 to 40-p-N selects a downstream optical signal addressed to the subscriber terminal from the received wavelength-multiplexed downstream signal. In this way, the subscriber terminal 40-p-n receives an optical signal of the wavelength λ1n from the link end #n.
The subscriber terminal 40-p-n transmits an upstream optical signal of a wavelength λ2n. Each power splitter 55-n wavelength-multiplexes the upstream optical signal of the wavelength λ2n input from the subscriber terminal 40-p-n with an upstream optical signal transmitted through the transmission line 50-1-p. The optical switch 1006 receives the wavelength-multiplexed signal, into which the upstream optical signals of the wavelengths λ21 to λ2N are wavelength-multiplexed, from the port 11-1-p. The optical switch 1006 outputs the wavelength-multiplexed upstream signal to the transmission line 50-2-q from the output destination port 11-2-q. The WDM device 97 receives the wavelength-multiplexed signal from the transmission line 50-2-q and wavelength-demultiplexes the wavelength-multiplexed upstream optical signal. The WDM device 97 outputs the upstream optical signal of the wavelength λ2n to a transmission line 50-2-q-n connected to the link end #n. In this way, the optical signal of the wavelength λ2n transmitted by the subscriber terminal 40-p-n is transmitted to the link end #n.
The WDM access ring network 31 is a network in which R add/drop nodes 32 are connected by transmission lines 53.
Each add/drop node 32 includes a demultiplexing unit 33, an optical switch 34, and a multiplexing unit 35. The demultiplexing unit 33 of the add/drop node 32-r (where r is an integer of 2 or more and R or less) demultiplexer a wavelength-multiplexed optical signal input from a transmission line 53-(r−1) and outputs optical signals obtained through the demultiplexing to the optical switch 34. The optical switch 34 is connected to one or more subscriber terminals 40.
Thus, an ONU #1 which is a subscriber terminal 40 connected to the add/drop node 32-4 of the WDM access ring network 31 and an ONU #2 which is a subscriber terminal 40 connected to ports 11-2-1 and 11-2-2 of the optical switch 1007 communicate as follows.
The ONU #1 transmits an optical signal of a wavelength to the add/drop node 32-4. The multiplexing unit 35 of the add/drop node 32-4 multiplexes the optical signal of the wavelength received by the optical switch 34 and optical signals not dropped by the optical switch 34 and outputs the multiplexed optical signal to the add/drop node 32-1. The optical switch 34 of the add/drop node 32-1 drops the optical signal of the wavelength λ1 demultiplexed by the demultiplexing unit 33 and outputs optical signals that have not been dropped to the multiplexing unit 35. The port 11-1-p1 of the optical switch 1007 receives the optical signal of the wavelength λ1 dropped by the add/drop node 32-1 from the transmission line 50-1-p1. The optical switch 1007 outputs the optical signal of the wavelength received from the port 11-1-p1 from the port 11-2-1. The optical receiver 43 of the ONU #2 receives the optical signal of the wavelength λ1 transmitted through the transmission line 50-2-1.
The optical transmitter 42 of the ONU #2 transmits a downstream optical signal of a wavelength λ2. The port 11-2-2 of the optical switch 1007 receives the optical signal transmitted by the ONU #2 from the transmission line 50-2-2. The optical switch 1007 outputs the downstream optical signal of the wavelength λ2 received from the port 11-2-2 from the port 11-1-p2. The optical switch 34 of the add/drop node 32-1 receives the optical signal of the wavelength λ2 output by the optical switch 1007 from the transmission line 50-1-p2 and outputs the received optical signal and optical signals that have not been dropped to the multiplexing unit 35. The optical signal of the wavelength λ2 is input to the add/drop node 32-4 via the add/drop nodes 32-2 and 32-3. The optical switch 34 of the add/drop node 32-4 drops the optical signal of the wavelength λ2. The optical receiver 43 of the ONU #1 receives the optical signal of the wavelength λ2 dropped by the add/drop node 32-4.
The add/drop node 32-1 of the WDM access ring network 31 and the WDM device 89 are connected by transmission lines 93-1 to 93-N (where N is an integer of 2 or more). The WDM device 89 receives upstream optical signals of wavelengths λn1 from transmission lines 93-n1 (where n1=1, 3, 5, N−1) and outputs a multiplexed signal, into which the received upstream optical signals are multiplexed, to a multiplexed communication transmission line 91. The WDM device 89 demultiplexes a wavelength-multiplexed downstream optical signal received via the multiplexed communication transmission line 91 and inputs the demultiplexed downstream optical signals of the wavelengths λn2 to the transmission lines 93-n2 (where n2=2, 4, 6, . . . , N).
The WDM device 81 demultiplexes the wavelength-multiplexed upstream optical signal received via the multiplexed communication transmission line 91 and inputs the demultiplexed upstream optical signals of the wavelengths λn1 to the ports 11-1-n1. The WDM device 81 receives downstream optical signals of wavelengths λn2 output from the ports 11-1-pn2, multiplexes the received downstream signals, and outputs the multiplexed signal to the multiplexed communication transmission line 91.
Thus, ONU #1 which is a subscriber terminal 40 connected to the add/drop node 32-4 of the WDM access ring network 31 and ONU #2 which is a subscriber terminal 40 connected to ports 11-2-1 and 11-2-2 of the optical switch 1008 communicate as follows. A case where N=18 will be described as an example.
The ONU #1 transmits an upstream optical signal of a wavelength λ1 to the add/drop node 32-4. Other ONUs also transmit upstream optical signals of wavelengths λ3 and λ5 to the add/drop node 32-4. The optical switch 34 of the add/drop node 32-4 receives the optical signals of the wavelengths λ1, λ3, and λ5. The multiplexing unit 35 of the add/drop node 32-4 multiplexes the optical signals of the wavelengths λ1, λ3, and λ5 received by the optical switch 34 and optical signals not dropped by the optical switch 34 and outputs the multiplexed optical signal to the add/drop node 32-1. The optical switch 34 of the add/drop node 32-1 drops the optical signals of the wavelengths λ1, λ3, λ5, . . . , λ17 demultiplexed by the demultiplexing unit 33 and outputs optical signals that have not been dropped to the multiplexing unit 35. The WDM device 89 outputs a multiplexed signal, into which the upstream optical signals of the wavelengths λ1, λ3, λ5, . . . , λ17 received from the transmission lines 93-1, 93-3, 93-5, . . . , 93-17 are multiplexed, to the multiplexed communication transmission line 91.
The WDM device 81 receives the wavelength-multiplexed upstream optical signal from the multiplexed communication transmission line 91 and wavelength-demultiplexes the wavelength-multiplexed upstream optical signal. The WDM device 81 transmits the upstream optical signals of the wavelengths λ1, λ3, λ5, . . . , λ17 to the ports 11-1-p1, 11-1-p3, 11-1-p5, 11-1-p17 of the optical switch 1008, respectively. The optical switch 1008 outputs the upstream optical signal of the wavelength i from the output destination port 11-2-1. The optical receiver 43 of the ONU #2 receives the optical signal of the wavelength λ1 transmitted through the transmission line 50-2-1.
The optical transmitter 42 of the ONU #2 transmits a downstream optical signal of a wavelength λ2. The port 11-2-2 of the optical switch 1008 receives the optical signal transmitted by the ONU #2 from the transmission line 50-2-2. The optical switch 1008 outputs the downstream optical signal of the wavelength λ2 received from the port 11-2-2 from the port 11-1-p2. The optical switch 1008 outputs the downstream optical signals of the wavelengths λ4, λ6, . . . , λ18 received respectively from the ports 11-2-4, 11-2-6, . . . , 11-2-18, to the ports 11-1-p4, 11-2-p6, . . . , 11-2-p18.
The WDM device 81 outputs a wavelength-multiplexed signal, into which optical signals of the wavelengths λ2, λ4, λ6, . . . , λ18 output from the ports 11-1-p 2, 11-1-p 4, 11-1-p6, . . . , 11-1-p 18 are multiplexed, to the multiplexed communication transmission line 91. The WDM device 89 demultiplexer the wavelength-multiplexed signal transmitted through the multiplexed communication transmission line 91 and outputs downstream optical signals of the wavelengths λ2, λ4, λ6, . . . , And λ18 obtained through the demultiplexing respectively to the transmission lines 93-2, 93-4, 93-6, . . . , 93-18. The optical switch 34 of the add/drop node 32-1 receives the optical signals of the wavelengths λ2, λ4, λ6, . . . , λ18 output by the WDM device 89 respectively from the transmission lines 93-2, 93-4, 93-6, . . . , 93-18 and outputs the received optical signals and optical signals that have not been dropped to the multiplexing unit 35. The multiplexing unit 35 multiplexes the optical signals input from the optical switch 34 and outputs the multiplexed optical signal to the transmission line 53-1.
The demultiplexing unit 33 of the add/drop node 32-2 demultiplexes the optical signal input from the transmission line 53-1 and outputs the demultiplexed signals to the optical switch 34. The optical switch 34 drops optical signals of wavelengths λ14, λ16, and λ18 corresponding to the add/drop node 32-2. The optical signals of the wavelengths λ14, λ16, and λ18 are transmitted to optical receivers 43 of subscriber terminals 40 corresponding to the wavelengths. The optical switch 34 of the add/drop node 32-2 receives optical signals of wavelengths λ13, λ15, and λ17 transmitted by the optical transmitters 42 of the subscriber terminals 40 and outputs the received optical signals and optical signals that have not been dropped to the multiplexing unit 35. The multiplexing unit 35 multiplexes the optical signals input from the optical switch 34 and outputs the multiplexed optical signal to the transmission line 53-2.
The add/drop node 32-3 operates in the same manner as the add/drop node 32-2. However, the optical switch 34 of the add/drop node 32-3 drops optical signals of wavelengths λ8, λ10, and λ12 corresponding to the add/drop node 32-3 and receives optical signals of wavelengths λ7, λ9, and λ11. The demultiplexing unit 33 of the add/drop node 32-4 demultiplexes a wavelength-multiplexed optical signal input from the transmission line 53-3 and outputs the demultiplexed signals to the optical switch 34. The optical switch 34 of the add/drop node 32-4 drops optical signals of wavelengths λ2, λ4, and λ6 corresponding to the add/drop node 32-4. The optical receiver 43 of the ONU #1 receives the optical signal of the wavelength λ2 dropped by the optical switch 34 of the add/drop node 32-4.
A transmission line 54 connected to the optical switch 1009a will be referred to as a transmission line 54a, two ports 11-1 connected to the transmission line 54a will be referred to as ports 11a-1-p1 and 11a-1-p2, a transmission line 54 connected to the optical switch 1009b will be referred to as a transmission line 54b, and two ports 11-1 connected to the transmission line 54b will be referred to as ports 11b-1-p1 and 11b-1-p2. N power splitters 57 connected to the transmission line 54a will be referred to as power splitters 57a-1 to 57a-N (where N is an integer of 1 or more) and M power splitters 57 connected to the transmission line 54b will be referred to as power splitters 57b-1 to 57b-M (where M is an integer of 1 or more). A multiplexer 82 and a demultiplexer 83 connected to a power splitter 57a-n (where n is an integer of 1 or more and N or less) will be referred to as a multiplexer 82a-n and a demultiplexer 83a-n, respectively, and a multiplexer 82 and a demultiplexer 83 connected to a power splitter 57b-m (where m is an integer of 1 or more and M or less) will be referred to as a multiplexer 82b-m and a demultiplexer 83b-m, respectively. An optical switch 95 connected to a multiplexer 82a-n will be referred to as an optical switch 95a-n and an optical switch 96 connected to a demultiplexer 83a-n will be referred to as an optical switch 96a-n. An optical switch 95 connected to a multiplexer 82b-m will be referred to as an optical switch 95b-m and an optical switch 96 connected to a demultiplexer 83b-m will be referred to as an optical switch 96b-m.
The optical switch 1009a and the optical switch 1009b are connected by a transmission line 54c and a transmission line 54d. A port 11-2 of the optical switch 1009a connected to the transmission line 54c will be referred to as a port 11a-2-q1 and a port 11-2 of the optical switch 1009a connected to the transmission line 54d will be referred to as a port 11a-2-q2. A port 11-2 of the optical switch 1009b connected to the transmission line 54c will be referred to as a port 11b-2-q1 and a port 11-2 of the optical switch 1009b connected to the transmission line 54d will be referred to as a port 11b-2-q2.
In the above configuration, an optical switch 95b-m outputs optical signals of different wavelengths transmitted by optical transmitters 42 of subscriber terminals 40 to ports of a multiplexer 82b-m corresponding to the wavelengths. The multiplexer 82b-m receives the optical signals of different wavelengths transmitted by the optical transmitters 42 of the subscriber terminals 40 via the optical switch 95b-m and outputs a wavelength-multiplexed optical signal into which the received optical signals are multiplexed. A power splitter 57b-m multiplexes the wavelength-multiplexed optical signal output by the multiplexer 82b-m with a wavelength-multiplexed optical signal that is transmitted through the transmission line 54b in a direction from the port 11b-1-p2to the port 11b-1-p1 and outputs the multiplexed optical signal.
The port 11b-1-p1 of the optical switch 1009b receives the wavelength-multiplexed optical signal from the transmission line 54b and the port 11b-2-q1 thereof outputs the received optical signal. The port 11a-2-q1 of the optical switch 1009a receives the wavelength-multiplexed optical signal output from the port 11b-2-q1 of the optical switch 1009b from the transmission line 54c. The optical switch 1009a outputs the wavelength-multiplexed optical signal input from the port 11a-2-q1 to the transmission line 54a from the port 11a-1-p1.
A power splitter 57a-n splits off the wavelength-multiplexed optical signal that is transmitted through the transmission line Ma in a direction from the port 11a-1-p1 to the port 11a-1-p2 and outputs the split wavelength-multiplexed optical signal to a demultiplexer 83a-n. The demultiplexer 83a-n demultiplexes the wavelength-multiplexed optical signal received from the power splitter 57a-n and outputs the demultiplexed optical signals to an optical switch 96a-n from ports corresponding to their wavelengths. The optical switch 96a-n outputs the optical signals of the wavelengths input from the demultiplexer 83a-n to optical receivers 43 of subscriber terminals 40 that are to receive optical signals of the wavelengths.
On the other hand, an optical switch 95a-n outputs optical signals of different wavelengths transmitted by optical transmitters 42 of subscriber terminals 40 to ports of a multiplexer 82a-n corresponding to the wavelengths. The multiplexer 82a-n receives the optical signals of different wavelengths transmitted by the optical transmitters 42 of the subscriber terminals 40 via the optical switch 95a-n and outputs a wavelength-multiplexed optical signal into which the received optical signals are multiplexed. A power splitter 57a-n multiplexes the wavelength-multiplexed optical signal output by the multiplexer 82a-n with a wavelength-multiplexed optical signal that is transmitted through the transmission line Ma in a direction from the port 11a-l-pl to the port 11a-1-p2.
The port 11a-1-p2 of the optical switch 1009a receives the wavelength-multiplexed optical signal from the transmission line Ma and the port 11a-2-q2 thereof outputs the received optical signal. The port 11b-2-q2 of the optical switch 1009b receives the wavelength-multiplexed optical signal output from the port 11a-2-q2 of the optical switch 1009a from the transmission line 54d. The optical switch 1009b outputs the wavelength-multiplexed optical signal input from the port 11b-2-q2 to the transmission line 54b from the port 11b-1-p2.
A power splitter 57b-m splits off the wavelength-multiplexed optical signal that is transmitted through the transmission line 54b in a direction from the port 11b-1-p2 to the port 11b-1-p1 and outputs the split wavelength-multiplexed optical signal to a demultiplexer 83b-m. The demultiplexer 83b-m demultiplexes the wavelength-multiplexed optical signal received from the power splitter 57b-m and outputs the demultiplexed optical signals to the optical switch 96b-m from ports corresponding to their wavelengths. The optical switch 96b-m outputs the optical signals of the wavelengths input from the demultiplexer 83b-m to optical receivers 43 of subscriber terminals 40 that are to receive optical signals of the wavelengths.
Although
Next, connection configurations when the number of user connections increases will be described.
When the number of users becomes great and thus the number of ONUs increases, the scale that the optical switch 1010 can accommodate may be exceeded. Even in such a case, through a connection configuration as illustrated in
A plurality of ports 11-1 of an optical switch 1010 will be referred to as ports 11-1-1, 11-1-2, 11-1-3, . . . , 11-1-p l, 11-1-p 2, and 11-1-p 3. A plurality of ports 11-2 of an optical switch 1010 will be referred to as ports 11-2-1, 11-2-2, 11-2-3, . . . , 11-2-q1, 11-2-q2, and 11-2-q 3.
In
For example, when the ONU #11 transmits an upstream optical signal of a wavelength addressed to an uplink #41, the optical switch 1010-1 outputs the optical signal input from the port 11-1-1 from the port 11-2-q 3. The port 11-1-p1 of the optical switch 1010-4 receives the optical signal of the wavelength output from the port 11-2-q3 of the optical switch 1010-1 and the port 11-2-1 thereof outputs the received signal.
When the ONU #12 transmits an upstream optical signal of a wavelength λ2 addressed to the ONU #31, the optical switch 1010-1 outputs the optical signal input from the port 11-1-2 from the port 11-2-q2. The port 11-1-p1 of the optical switch 1010-3 receives the optical signal output from the port 11-2-q2 of the optical switch 1010-1. The optical switch 1010-3 performs the same return communication of the optical signal of the wavelength λ2 input from the port 11-1-p1 as that which the optical switch 10b illustrated in
In
For example, when the ONU #11 transmits an upstream optical signal of a wavelength addressed to an uplink #41, the optical switch 1010-1 outputs an optical signal input from the port 11-1-1 from the port 11-2-q l. The port 11-1-p1 of the optical switch 1010-2 receives the optical signal output from the port 11-2-q1 of the optical switch 1010-1 and the optical signal is output from the port 11-2-q1 thereof according to the wavelength 4 The port 11-1-p1 of the optical switch 1010-3 receives the optical signal output from the port 11-2-q1 of the optical switch 1010-2 and the optical signal is output from the port 11-2-q1 thereof according to the wavelength 4 The port 11-1-p1 of the optical switch 1010-4 receives the optical signal output from the port 11-2-q1 of the optical switch 1010-3 and the optical signal is output from the port 11-2-1 thereof according to the wavelength λ1.
When the ONU #12 transmits an upstream optical signal of a wavelength λ2 addressed to the ONU #31, the optical switch 1010-1 outputs an optical signal input from the port 11-1-2 from the port 11-2-q2. The port 11-1-p2of the optical switch 1010-2 receives the optical signal output from the port 11-2-q2 of the optical switch 1010-1. The optical switch 1010-2 outputs the optical signal input from the port 11-1-p2 from the port 11-2-q2 according to the wavelength λ2. The port 11-1-p2 of the optical switch 1010-3 receives the optical signal output from a port 11-2-q2 of the optical switch 1010-2. The optical switch 1010-3 performs the same return communication of the optical signal input from the port 11-1-p2 according to the wavelength λ2 as that which the optical switch 10b illustrated in
In each of the following embodiments, examples of an optical access system using the optical switch having the functions described above will be described.
Subscriber terminals 40 are devices on the optical subscriber side. Subscriber terminals 40 are connected to the optical gateway 200 via transmission lines 501. Each transmission line 501 is, for example, an optical fiber. The optical gateway 200 is an apparatus in a communication station. The subscriber terminals 40 and the optical gateway 200 are connected, for example, via transmission lines 501 or power splitters 502 as indicated by reference sign N1. A network configuration for connecting the subscriber terminals 40 to the optical gateway 200 may be of various network topologies such as point-to-point (P to P), a PON configuration, and a bus configuration. An example may be a configuration in which transmission lines 501 are provided with power splitters 502 or the like, such that a plurality of subscriber terminals 40 are connected to each transmission line 501. The optical gateway 200 is connected to other stations, a core network, or the like via transmission lines 511 and the transmission lines 512. The transmission lines 511 and the transmission lines 512 are each, for example, an optical fiber. The transmission lines 511 transmit upstream signals and the transmission lines 512 transmit downstream signals. The transmission lines 511 and the transmission lines 512 are each an example of a multiplexed communication transmission line that transmits a wavelength-multiplexed optical signal. A connection from the optical gateway 200 to another station or the core network indicated by reference sign N2 is provided, for example, by a transmission line 511 or 512 which is an optical fiber. Here, connections between link ends are made to form a full mesh. The present embodiment will be described with reference to an example in which the optical gateway 200 is installed in a station of a link end A and connected to an optical communication apparatus set in a station of a link end B and an optical communication apparatus installed in a station of a link end C via an optical communication network 30 or the like. The optical communication apparatuses of the link ends B and C to which the optical gateway 200 is connected may be optical gateways 200.
The subscriber terminals 40 are connected to the optical gateway 200 via transmission lines 501. Each subscriber terminal 40 includes an optical transceiver 41. The optical transceiver 41 is a wavelength-variable optical transceiver. The optical transceiver 41 is, for example, an optical transceiver that converts an optical signal and an electrical signal into each other. Each subscriber terminal 40 can select and set its own wavelength in the optical transceiver 41 according to a transmission/reception destination. The subscriber terminal 40 sets the wavelength to be used in the optical transceiver 41 according to an instruction received from the optical gateway 200. M subscriber terminals 40 connected to the optical gateway 200 (where M is an integer of 1 or more) will be referred to as subscriber terminals 40-1 to 40-M.
The optical gateway 200 includes an optical switch 210, wavelength multiplexers/demultiplexers 220, a control device 230, multiplexers 241 and demultiplexers 242, splitting portions 250, and a monitoring device 260. The splitting portions 250 and the monitoring device 260 are examples of a monitoring unit.
The optical switch 210 has a plurality of input/output ports (hereinafter referred to as “ports”) and connects two or more ports. The optical switch 210 can freely switch optical paths between ports. Ports for receiving or outputting upstream signals will be referred to as upstream ports and ports for receiving or outputting downstream signals will be referred to as downstream ports. Each port of the optical switch 210 is connected to a transmission line.
Each wavelength multiplexer/demultiplexer 220 performs upstream and downstream multiplexed separation to separate an upstream signal and a downstream signal according to the wavelength. The wavelength multiplexer/demultiplexer 220 receives an upstream optical signal transmitted by a subscriber terminal 40 from a transmission line 501 and outputs an upstream optical signal to the optical switch 210 via a transmission line 521. The wavelength multiplexer/demultiplexer 220 also receives a downstream optical signal output by the optical switch 210 from a transmission line 522 and outputs the downstream optical signal to the subscriber terminal 40 via the transmission line 501.
The control device 230 is connected to an upstream port and a downstream port to which no subscriber terminals 40 are connected among the ports of the optical switch 210. The upstream port of the optical switch 210 is connected to a transmitting port of the control device 230 by a transmission line 531. The downstream port of the optical switch 210 is connected to a transmitting port of the control device 230 by a transmission line 533. The control device 230 includes a wavelength demultiplexer 231, optical receivers (Rx) 232 for wavelength channels, and a wavelength-variable transmitter 233. The wavelength demultiplexer 231 is, for example, arrayed waveguide gratings (AWG). The wavelength demultiplexer 231 demultiplexer light, which has been input to its receiving port via the transmission line 540, into light beams corresponding to the wavelengths. The wavelength demultiplexer 231 outputs the demultiplexed light beams to the optical receivers 232 that are to receive optical signals of the wavelengths of the light beams. The wavelength-variable transmitter 233 includes a wavelength-variable laser diode (LD) that generates light of a variable wavelength. The wavelength-variable transmitter 233 transmits an optical signal of a variable wavelength by using light generated by the wavelength-variable laser diode. The wavelength-variable transmitter 233 outputs an optical signal using the generated light from the transmitting port to the transmission line 533.
Each multiplexer 241 multiplexes upstream optical signals of different wavelengths that the optical switch 210 has output from a plurality of transmission lines 541 and outputs the multiplexed optical signal to a transmission line 511 connected to another link end. Each demultiplexer 242 receives an optical signal transmitted from another link end from a transmission line 512 and wavelength-demultiplexer the received downstream optical signal. The demultiplexer 242 inputs the demultiplexed downstream optical signals to the optical switch 210 via a plurality of transmission lines 542 connected to upstream ports corresponding to the wavelengths of the optical signals.
A splitting portion 250 is provided on transmission lines 511 and 512. The splitting portion 250 includes power splitters 251 and 252. The power splitter 251 splits off an upstream optical signal transmitted through the transmission line 511 and inputs the split upstream optical signal to the optical switch 210 via a transmission line 551. The power splitter 252 splits off a downstream optical signal transmitted through the transmission line 512 and inputs the split downstream optical signal to the optical switch 210 via a transmission line 552.
The monitoring device 260 includes a wavelength demultiplexer 261 and optical receivers (Rx) 262 for wavelengths. The wavelength demultiplexer 261 is connected to the optical switch 210 via a transmission line 560. The optical switch 210 outputs an optical signal received from a port connected to the transmission line 541 or 542 to a port connected to the transmission line 560. In this way, the wavelength demultiplexer 261 receives an optical signal split off by the splitting portion 250. The wavelength demultiplexer 261 demultiplexer the received optical signal into signals corresponding to the wavelengths. The wavelength demultiplexer 261 outputs the demultiplexed light beams to the optical receivers 262 that are to receive optical signals of the wavelengths of the light beams. The monitoring device 260 monitors communication states involving transmission and reception of the subscriber terminals 40 based on optical signals received by the optical receivers 262.
The OPS 300 includes an optical gateway control unit 301 and a management database (DB) 350. The optical gateway control unit 301 is connected to the optical gateway 200. The optical gateway control unit 301 includes a wavelength control unit 310 and an optical switch control unit 320. The wavelength control unit 310 stores information indicating the wavelength of light used by each user (or each service). The wavelength control unit 310 dynamically assigns each user a wavelength to be used by the user with reference to this information. The wavelength control unit 310 may be installed in a building different from that of the optical gateway 200 and may be connected to the optical switch 210 or the optical switch control unit 320 via a network. By sharing each piece of connection information, the wavelength control unit 310 manages and controls information on which user is connected to which port of the optical switch 210 and which wavelength is being used in real time.
The optical gateway control unit 301 is connected to the management database 350. The optical gateway control unit 301 exchanges information on users and used wavelengths with the management database 350. The management database 350 stores used wavelengths and destination information of users. The destination is represented, for example, by a link end A or B. The management database 350 manages information on all users connected to the optical access system 100.
The wavelength table includes a user wavelength table and an inter-station wavelength table.
Subsequently, exemplary configurations of a subscriber terminal 40 will be described with reference to
Here, an operation when a subscriber terminal 40 is newly connected will be described.
First, a user request is made before a new subscriber terminal 40-1 is connected. For example, by a user request, it is permitted to perform communication between the link ends A and B. Based on the user request, a service provider registers user information, initial destination information, and the like in the management database 350 of the OPS 300 (step Si). The user information is, for example, information that makes it possible to obtain a wavelength that can be used by the optical transceiver 41. The OPS 300 refers to the switch connection table and assigns ports of the optical switch 210 to which the subscriber terminal 40-1 is to be connected from idle ports of the optical switch 210. Here, upstream and downstream ports are assigned. The OPS 300 registers information indicating that the assigned ports are connected to the subscriber terminal 40-1 in the switch connection table (step S2). The optical switch control unit 320 of the OPS 300 controls the optical switch 210 such that optical signals are transmitted and received between the ports assigned to the subscriber terminal 40-1 and ports to which the control device 230 is connected.
When the new subscriber terminal 40-1 is connected, the subscriber terminal 40-1 performs initialization processing and transmits a connection request (a register request) by an optical signal (step S3). The subscriber terminal 40-1 automatically performs the initialization process before or immediately after the connection. A wavelength multiplexer/demultiplexer 220 receives the connection request from a transmission line 501 and outputs the connection request to the optical switch 210 via a transmission line 521. The optical switch 210 transmits the connection request received from a port connected to the subscriber terminal 40-1 to an output port to which the control device 230 is connected. The control device 230 receives the connection request from a receiving port via a transmission line 531. The control device 230 analyzes the received optical signal and checks, for example, whether there is a problem with the initially set wavelength or optical power (step S4).
The control device 230 transmits a restart or initialization instruction to the subscriber terminal 40-1 when there is a problem with the wavelength or optical power. After restarting or initial setting, the process returns to step S3 and the subscriber terminal 40-1 transmits a connection request again.
The control device 230 analyzes an optical signal received from the subscriber terminal 40-1, and if it is confirmed that there is no problem, outputs a connection request to the optical gateway control unit 301. The optical gateway control unit 301 registers information on the subscriber terminal 40-1 in the management database 350. The connection request includes connection source information, connection destination information, the type of a signal to be transmitted, and the like. For example, address information such as a medium access control (MAC) address is used as the connection source information. For example, address information of the destination is used as the connection destination information. For example, a service or a modulation method is used as the type of signal to be transmitted. Based on such information, the wavelength control unit 310 registers the connection source information in the management database 350. In this way, an identification of the user who uses the subscriber terminal 40-1 and information indicating that the wavelength that can be used by the subscriber terminal 40-1 is idle are set in the user wavelength table. Further, the wavelength control unit 310 calculates an optimal path between the subscriber terminal 40-1 and the communication destination, such as between the link ends A and B by checking such information with connection information stored in the management database 350. The wavelength control unit 310 searches for “idle” indicated by the inter-station wavelength table according to the calculated path. The wavelength control unit 310 selects a wavelength to be used by the subscriber terminal 40-1 from the idle wavelengths and transmits information on the selected wavelength to the control device 230 (step S5).
Another subscriber terminal 40 which is a communication destination of the subscriber terminal 40-1 will be referred to as a communication destination subscriber terminal 40. In this case, the wavelength control unit 310 selects a transmission wavelength which is a wavelength to be used by the subscriber terminal 40-1 to transmit an optical signal to the communication destination subscriber terminal 40 and a reception wavelength which is a wavelength to be used by the subscriber terminal 40-1 to receive an optical signal from the communication destination subscriber terminal 40. The wavelength control unit 310 transmits the selected transmission and reception wavelengths to the control device 230 as wavelengths to be used by the subscriber terminal 40-1. When the subscriber terminal 40-1 performs only transmission to the communication destination subscriber terminal 40, the wavelength control unit 310 does not have to select the reception wavelength. Further, when the subscriber terminal 40-1 performs only reception from the communication destination subscriber terminal 40, the wavelength control unit 310 does not have to select the transmission wavelength.
The control device 230 transmits wavelength information as follows. The wavelength-variable transmitter 233 of the control device 230 transmits a wavelength instruction, in which information on a wavelength selected by the wavelength control unit 310 is set, by an optical signal of a wavelength indicating that it is addressed to the subscriber terminal 40-1. The optical switch 210 outputs the optical signal received from a port connected to the wavelength-variable transmitter 233 to a transmission line 522 connected to the subscriber terminal 40-1. The wavelength multiplexer/demultiplexer 220 inputs the optical signal, which has been received from the optical switch 210 via the transmission line 522, to a transmission line 501. The subscriber terminal 40-1 receives the optical signal transmitted through the transmission line 501. The subscriber terminal 40-1 sets an oscillation wavelength of the optical transceiver 41 according to the wavelength instruction indicated by the received optical signal (step S6). That is, the subscriber terminal 40-1 sets the oscillation wavelength of the optical transceiver 41 (that of the wavelength-variable light source 451) such that it transmits optical signals of the transmission wavelength set in the wavelength instruction. When a reception wavelength has been set in the wavelength instruction, the subscriber terminal 40-1 sets the optical transceiver 41 (the wavelength-variable filter 452) such that it receives wavelength signals of the reception wavelength.
The optical transceiver 41 of the subscriber terminal 40-1 transmits a notification signal notifying that the wavelength has been set by the optical signal of the instructed wavelength. The notification signal is transmitted to the control device 230 in the same manner as the request signal. Based on the received notification signal, the control device 230 checks whether the designated wavelength has been correctly set, whether the output power is sufficient, and the like (step S7). Upon determining that there is no problem as a check result, the control device 230 transmits a permission notification indicating permission to start communication to the subscriber terminal 40-1 by an optical signal. The permission notification is transmitted to the subscriber terminal 40-1 in the same manner as the wavelength instruction.
The optical switch control unit 320 transmits connection information on optimal ports of the optical switch 210 to the optical switch 210 according to the forwarding destination of the subscriber terminal 40-1. Based on the connection information, the optical switch 210 sets an upstream port and a downstream port for the subscriber terminal 40-1 according to an instruction from the optical switch control unit 320 (step S8).
The optical access system 100 performs timing controls such that the optical switch 210 performs path switching after the permission to start communication is transmitted from the control device 230 to the subscriber terminal 40-1. For example, it is assumed that the time required for the optical switch 210 to perform path switching is known in advance. In this case, the control device 230 waits until the subscriber terminal 40-1 actually starts communication after receiving the permission to start communication. Here, the waiting time is the time required for the optical switch 210 to actually perform path switching after receiving a path switching instruction. After that, the control device 230 issues an instruction to start communication. After communication starts, the monitoring device 260 of the optical gateway 200 checks the confirmation of the communication status between opposing subscriber terminals (step S9). The monitoring device 260 notifies the OPS 300 of the check result. If the check result indicates an error, the OPS 300 performs a cause isolation procedure.
The connection request transmitted by the subscriber terminal 40-1 and the control signal that the control device 230 transmits to the subscriber terminal 40-1 are optical signals slower than main signals. For example, a protocol-free control signal (control method) represented by AMCC can be used as the control signal.
Further, the OPS 300 instructs the communication destination subscriber terminal 40 to use the transmission wavelength for the subscriber terminal 40-1 as a reception wavelength for the communication destination subscriber terminal 40 and the reception wavelength for the subscriber terminal 40-1 as a transmission wavelength for the communication destination subscriber terminal 40. For example, in an optical gateway control unit 301 that controls an optical gateway 200 in which the communication destination subscriber terminal 40 is accommodated, a wavelength control unit 310 instructs a control device 230 to transmit a wavelength instruction in which the reception wavelength and the transmission wavelength for the communication destination subscriber terminal 40 are set. The communication destination subscriber terminal 40 receives the wavelength instruction from the control device 230 by a control signal and sets the reception and transmission wavelengths in its optical transceiver 41 according to the received wavelength instruction. That is, when a transmission wavelength has been set in the wavelength instruction, the communication destination subscriber terminal 40 sets an oscillation wavelength of the optical transceiver 41 (that of the wavelength-variable light source 451) such that it transmits optical signals of the transmission wavelength. When a reception wavelength has been set in the wavelength instruction, the communication destination subscriber terminal 40 sets the optical transceiver 41 (the wavelength-variable filter 452) such that it receives wavelength signals of the reception wavelength.
In the optical access system 100, without making a user request in step Si, information to be registered in the management database 350 by the user request may be transmitted and received between the new subscriber terminal 40-1 and the optical gateway control unit 301. This allows the subscriber terminal 40-1 to communicate with another subscriber terminal 40 without making a user request. Transmission and reception of information between the subscriber terminal 40-1 and the optical gateway control unit 301 are performed via the control device 230, for example, using AMCC.
The operation when a new subscriber terminal is connected has been described above. Next, a normal communication operation after a new subscriber terminal is connected will be described with reference to the case where the subscriber terminal 40-2 of
First, an upstream optical signal will be described. An upstream optical signal output by the subscriber terminal 40-2 is transmitted to the optical gateway 200 via a transmission line 501. The wavelength multiplexer/demultiplexer 220 of the optical gateway 200 separates input optical signals into an upstream optical signal and a downstream optical signal according to their wavelengths. The upstream optical signal demultiplexed by the wavelength multiplexer/demultiplexer 220 is input to the optical switch 210 via a transmission line 521. The optical switch 210 outputs the optical signal by connecting a port to which the upstream optical signal is input from the wavelength multiplexer/demultiplexer 220 to another port according to a path to the destination of the subscriber terminal 40-2. When a wavelength is used as destination information, the optical switch 210 outputs the optical signal by connecting the port to another port corresponding to the destination identified by the wavelength assigned to the subscriber terminal 40-2. The upstream signal output from the optical switch 210 is multiplexed with optical signals of other wavelengths transmitted by other subscriber terminals 40 by the multiplexer 241 and the multiplexed optical signal is transmitted to another station (for example, the link end B) via a single transmission line 511. The multiplexer 241 multiplexes wavelength channels for each station such as each of the link ends B and C. Because the transmission line 511 between the optical gateway 200 and the link end B and the transmission line 511 between the optical gateway 200 and the link end C are separated, the same wavelength can be used for the link ends B and C.
Next, downstream communication will be described. Downstream is communication in a direction from the link end B or C to a subscriber terminal 40. A downstream optical signal is transmitted to the optical gateway 200 via a single transmission line 512. The demultiplexer 242 of the optical gateway 200 wavelength-demultiplexes the downstream optical signal transmitted through the transmission line 512. The demultiplexer 242 inputs the demultiplexed light beams to downstream ports corresponding to the wavelengths of the demultiplexed light beams via transmission lines 542. The optical switch 210 outputs each downstream optical signal by connecting a port to which the downstream optical signal is input from the demultiplexer 242 to another port according to the wavelength. The wavelength multiplexer/demultiplexer 220 separates optical signals, which have been input from the optical switch 210 via the transmission lines 522, into an upstream optical signal and a downstream optical signal according to their wavelengths. The downstream optical signal demultiplexed by the wavelength multiplexer/demultiplexer 220 is input to the subscriber terminal 40-2 via a transmission line 501. Here, it is assumed that wavelength channels transmitted from the optical gateway 200 to stations (such as the link ends B and C) are of the same wavelength band, although different wavelength bands may be used for stations.
The monitoring device 260 of the optical gateway 200 receives light beams split off by the splitting portions 250. Light beams split off by the splitting portions 250 are optical signals transmitted and received by subscriber terminals 40. The monitoring device 260 monitors the received optical signals to monitor signals transmitted and received by subscriber terminals 40. Upon detecting an abnormality such as a wavelength shift, a decrease in power, or a communication abnormality through monitoring, the monitoring device 260 transmits an abnormality detection signal to the optical gateway control unit 301. The optical switch control unit 320 of the optical gateway control unit 301 controls the optical switch 210 such that a corresponding subscriber terminal 40 is reconnected to the control device 230. Then, the optical gateway control unit 301 performs a process of assigning a new wavelength, different from the wavelength used when the abnormality has been detected, in the same manner as when the subscriber terminal 40 is newly connected. Thus, upon receiving an optical signal of the changed wavelength from the subscriber terminal 40, the optical switch 210 connects the received optical signal to the port that has been designated for the subscriber terminal 40 by the wavelength before the change.
The optical gateway 200 illustrated in
Each wavelength multiplexer/demultiplexer 243 separates input optical signals into an upstream optical signal and a downstream optical signal according to their wavelengths. The wavelength multiplexer/demultiplexer 243 separates an upstream optical signal input from the optical switch 210 via a transmission line 543-1 and transmits it to another link end or an upper level network via a transmission line 503. Each wavelength multiplexer/demultiplexer 243 also separates a downstream optical signal input from another link end via a transmission line 503 and outputs it to the optical switch 210 via a transmission line 543-2.
A splitting portion 250a is provided on each transmission line 503. The splitting portion 250a includes a power splitter 251a. The power splitter 251a splits off upstream and downstream optical signals transmitted through the transmission line 503. The power splitter 251a inputs the split upstream optical signal to a port of the optical switch 210 via a transmission line 551a and inputs the split downstream optical signal to a port of the optical switch 210 via a transmission line 551b. The optical switch 210 outputs the optical signal input from the port connected to the transmission line 551a and the optical signal input from the port connected to the transmission line 551b from a port connected to the transmission line 560. In this manner, the wavelength demultiplexer 261 of the monitoring device 260 receives optical signals split off by the splitting portion 250a.
Each wavelength multiplexer/demultiplexer 244 separates optical signals into an upstream optical signal and a downstream optical signal according to their wavelengths. The wavelength multiplexer/demultiplexer 244 inputs an upstream optical signal received from the optical switch 210 via a transmission line 544 to a wavelength multiplexer/demultiplexer 245 via a transmission line 545. The wavelength multiplexer/demultiplexer 244 inputs a downstream optical signal received from the wavelength multiplexer/demultiplexer 245 via a transmission line 546 to the optical switch 210 via the transmission line 544.
Each wavelength multiplexer/demultiplexer 245 separates optical signals into an upstream optical signal and a downstream optical signal according to their wavelengths. The wavelength multiplexer/demultiplexer 245 transmits an upstream optical signal, which has been received from a wavelength multiplexer/demultiplexer 245 via a transmission line 545, to another link end or an upper level network via a transmission line 503. The wavelength multiplexer/demultiplexer 245 inputs a downstream optical signal received via the transmission line 503 to the wavelength multiplexer/demultiplexer 244 via a transmission line 546.
Each splitting portion 250b includes a power splitter 251b and a power splitter 252b. The power splitter 251b splits off an upstream optical signal transmitted through a transmission line 545. The power splitter 251b inputs the split upstream optical signal to a port of the optical switch 210 via a transmission line 551b. The power splitter 252b splits off a downstream optical signal transmitted through a transmission line 546. The power splitter 252b inputs the split downstream optical signal to a port of the optical switch 210 via a transmission line 552b. The optical switch 210 outputs the optical signal input from the port connected to the transmission line 551b and the optical signal input from the port connected to the transmission line 552b from a port connected to the transmission line 560. In this manner, the wavelength demultiplexer 261 of the monitoring device 260 receives optical signals split off by the splitting portion 250b.
The monitoring device 260 described above has a receiver configuration including the wavelength demultiplexer 261 and the optical receivers 262 for wavelengths. The monitoring device may have a wavelength-variable optical receiver instead of this receiver configuration. Also, the transceiver of the control device may have a transmitter that is not wavelength-variable and may have a receiver configuration including no wavelength demultiplexer. An example of such a configuration will be described with reference to
The monitoring device may also be connected via an optical switch different from the optical switch described above. An example of such a configuration will be described with reference to
An upstream optical signal separated from a transmission line 511 by a power splitter 251 of a splitting portion 250 is input to the optical switch 211 via a transmission line 555 and a downstream optical signal separated from a transmission line 512 by a power splitter 252 is input to the optical switch 211 via a transmission line 555. The optical switch 211 is, for example, a small optical switch. The number of ports of the optical switch 211 is 1 on the monitoring device 260 side and 2M on the side where monitored optical signals are input. 2M is twice the number of M subscriber terminals 40 connected to the optical gateway 204. Also, instead of using a small optical switch, as many monitoring devices as the number of connected link ends may be provided to monitor signals transmitted to and received from all link ends on a per link end basis.
In the present embodiment, communication is performed between a plurality of subscriber terminals connected to the same optical gateway by using a return transmission line. Hereinafter, differences from the first embodiment will be mainly described.
Similar to each multiplexer 241, the multiplexer 247 multiplexes upstream optical signals of different wavelengths that the optical switch 210 outputs through a plurality of transmission lines 541 and outputs the multiplexed optical signal to the transmission line 547. Similar to a demultiplexer 242, the demultiplexer 248 wavelength-demultiplexes a downstream optical signal input from the transmission line 547. The demultiplexer 248 inputs the demultiplexed downstream optical signals to the optical switch 210 via a plurality of transmission lines 542 connected to downstream ports corresponding to the wavelengths of the optical signals. The transmission line 547 is also provided with a splitting portion 250.
In the first embodiment, subscriber terminals connected to the link end A are connected to ports for connection to the link ends B and C via the optical switch. In the present embodiment, another pair of a multiplexer and a demultiplexer which is the same as each pair of the multiplexer 241 and the demultiplexer 242 connected to the link ends B and C is added. This added pair is the multiplexer 247 and the demultiplexer 248. Then, an output port of the added multiplexer 247 and an input port of the added demultiplexer 248 are connected by the transmission line 547. This configuration allows a signal output by a subscriber terminal 40 to be input to the optical switch 210 again. Thus, in the optical gateway 205, an optical signal output by a subscriber terminal 40 is returned and input to the optical switch 210 again as a downstream signal. This return signal is connected to another subscriber terminal 40 within the optical switch 210, thereby enabling return communication, that is, communication between subscriber terminals 40 connected to the same optical gateway 205.
For example, a state where a subscriber terminal 40-2 and a subscriber terminal 40-M communicate with each other will be described. Here, it is assumed that K upstream ports of the optical switch 210 corresponding to the link end A are connected to the multiplexer 247 by transmission lines 541 and K downstream ports of the optical switch 210 corresponding to the link end A are connected to the multiplexer 248 by transmission lines 542 (where K is an integer of 2 or more). It is also assumed that a k-th downstream and upstream ports among the K downstream ports and upstream ports corresponding to the link end A corresponds to a wavelength (where k is an integer of 1 or more and K or less). An upstream optical signal of a wavelength output from the subscriber terminal 40-2 is connected to the first upstream port corresponding to the link end A. The optical signal input to the optical switch 210 is returned by the transmission line 547 and is input again to the optical switch 210 as a downstream optical signal from the first downstream port corresponding to the link end A. The optical switch control unit 320 sets a path within the optical switch 210 such that the optical signal is transmitted to the subscriber terminal 40-M according to the wavelength. Similarly, an upstream optical signal of a wavelength output from the subscriber terminal 40-M is connected to the k-th upstream port corresponding to the link end A. The optical signal input to the optical switch 210 is returned by the transmission line 547 and is input again to the optical switch 210 as a downstream optical signal from the k-th downstream port corresponding to the link end A. The optical switch control unit 320 sets a path within the optical switch 210 such that the optical signal is transmitted to the subscriber terminal 40-2 according to the wavelength. In this way, communication is performed between the subscriber terminal 40-2 and the subscriber terminal 40-M.
Other configurations of the present embodiment will be described with reference to
A power splitter may also be provided subsequent to the demultiplexer 248 of the optical gateway 205 in
While differences from the optical access system 103 have been described above, the differences can also be applied to the optical access systems 100, 101, and 102.
Optical access systems of the present embodiment perform multicast communication. In the present embodiment, differences from the first and second embodiments will be mainly described.
First, multicast for downstream communication will be described with reference to
A case where a downstream optical signal transmitted from the link end C is multicast will be described. The optical switch control unit 320 performs control such that a port for receiving a downstream optical signal from the link end C is connected to a return port to which the transmission line 549 is connected according to the wavelength. Thus, the downstream optical signal from the link end C is transmitted through the transmission line 549 and input to the optical switch 210 again as an upstream signal of the link end A. The optical switch control unit 320 also performs control such that the downstream optical signal input from the return port is connected to an upstream signal port for the link end A, similar to the second embodiment. Thus, the optical signal that has been returned by the transmission line 549 and input to the optical switch 210 is output to a port connected to the multiplexer 247. The multiplexer 247 multiplexes optical signals that are output from the optical switch 210 through a plurality of transmission lines 541 and outputs the multiplexed optical signal to the transmission line 547. The optical signal output to the transmission line 547 is split into a plurality of optical signals by the power splitter 270. The power splitter 270 inputs the plurality of split optical signals to the optical switch 210 as downstream signals of the link end A via a plurality of transmission lines 542. The optical switch 210 outputs the optical signals input from the transmission lines 542 to ports connected to subscriber terminals 40 according to their wavelengths. This enables multicast of a downstream signal.
Subsequently, multicast for upstream communication will be described with reference to
A case where an upstream optical signal transmitted from the link end A is multicast will be described. The optical switch control unit 320 performs control such that a port for receiving the upstream optical signal from the link end A is connected to a return port to which the transmission line 570 is connected according to the wavelength. Thus, the upstream optical signal from the link end A is transmitted through the transmission line 570 and input to the optical switch 210 again. The optical switch control unit 320 also performs control such that the optical signal input from a return port is output to a port connected to the power splitter 271. Thus, the optical signal that has been returned by the transmission line 570 and input to the optical switch 210 is output to the transmission line 572. The optical signal output to the transmission line 572 is split into a plurality of optical signals by the power splitter 271. The power splitter 271 inputs the plurality of split optical signals to the optical switch 210 as upstream signals via the plurality of transmission lines 573. The optical switch 210 outputs the optical signals input from the transmission lines 573 to ports connected to the link end B or C according to their wavelengths. This enables multicast of an upstream signal.
Subsequently, a configuration in which point-to-multipoint communication including upstream communication is performed while performing downstream communication multicast will be described with reference to
A case where a downstream optical signal transmitted from the link end C is multicast will be described. The optical switch control unit 320 performs control such that a port for receiving the downstream optical signal from the link end C is connected to a return port to which the transmission line 574 is connected according to the wavelength. Thus, the downstream optical signal from the link end C is transmitted through the transmission line 574 and input to the optical switch 210 again as an upstream signal of the link end A. The optical switch control unit 320 also performs control such that the downstream optical signal input from a return port is output to a port to which the power splitter 272 is connected. Thus, the optical signal that has been returned by the transmission line 574 and input to the optical switch 210 is output to the transmission line 581. The optical signal output to the transmission line 581 is split into a plurality of optical signals by the power splitter 272. The power splitter 272 inputs the plurality of split optical signals to the optical switch 210 as downstream signals via the plurality of transmission lines 582. The optical switch 210 outputs the optical signals input from the transmission lines 582 to ports connected to the subscriber terminal 40 according to their wavelengths. This enables multicast of a downstream signal.
A case where upstream optical signals transmitted from the link end A are transmitted to the link end C will be described. The optical switch control unit 320 performs control such that ports for inputting the upstream optical signals from the link end A are connected to ports to which the power splitter 273 is connected according to their wavelengths. Thus, the upstream optical signals from the link end A are output to the transmission lines 583. The optical signals output to the plurality of transmission lines 583 are multiplexed by the power splitter 273. The power splitter 273 inputs the multiplexed optical signal to the optical switch 210 via the transmission line 584. The optical switch 210 performs control such that the optical signal input from the transmission line 584 is connected to a return port to which the transmission line 575 is connected. Thus, the optical signal is transmitted through the transmission line 575 and input to the optical switch 210 again. The optical switch 210 outputs the optical signal input from the transmission line 575 to a multiplexer 241 connected to the link end C according to the wavelength.
The present embodiment provides two sets of configurations each using a power splitter for multicast as described above, thereby enabling not only downstream multicast communication but also point-to-multipoint communication including upstream communication.
In the present embodiment, communication is performed without separating an upstream signal and a downstream signal. Hereinafter, differences from the above embodiments will be mainly described.
Each wavelength multiplexer/demultiplexer 249 is connected to the optical switch 210 by a plurality of transmission lines 585. The wavelength multiplexer/demultiplexer 249 multiplexes upstream optical signals of different wavelengths that the optical switch 210 outputs through the plurality of transmission lines 585 and outputs the multiplexed optical signal to a transmission line 504 connected to another link end. The wavelength multiplexer/demultiplexer 249 wavelength-demultiplexes a downstream optical signal that has been input from another link end via the transmission line 504. The wavelength multiplexer demultiplexer 249 inputs the demultiplexed downstream optical signals to the optical switch 210 via the plurality of transmission lines 585 connected to upstream ports corresponding to the wavelengths of the optical signals.
Each splitting portion 253 includes a power splitter 254. The power splitter 254 splits off an upstream optical signal and a downstream optical signal transmitted through the transmission line 504. The power splitter 254 inputs the split upstream optical signal to a port of the optical switch 210 via a transmission line 586 and inputs the split downstream optical signal to a port of the optical switch 210 via a transmission line 587. The optical switch 210 outputs an optical signal input from a port connected to the transmission line 586 or the transmission line 587 to a port connected to a transmission line 560.
The wavelength multiplexer/demultiplexer 238 is connected to the optical switch 210 by a transmission line 534 and is connected to the control device 235 by a transmission line 531 and a transmission line 533. The wavelength multiplexer/demultiplexer 238 separates input optical signals into an upstream optical signal and a downstream optical signal according to their wavelengths. The wavelength multiplexer/demultiplexer 238 outputs an upstream optical signal, which has been input from the optical switch 210 via the transmission line 534, to the control device 235 via the transmission line 531. The wavelength multiplexer/demultiplexer 238 outputs a downstream optical signal, which has been input from the control device 235 via the transmission line 533, to the optical switch 210 via the transmission line 534.
The optical gateway 2011 does not include wavelength multiplexers/demultiplexers between the optical switch 210 and subscriber terminals 40 and does not separate an upstream signal and a downstream signal as described above. This can greatly reduce the number of ports used for the optical switch 210 and greatly reduce the amount of information to be managed. Further, as illustrated in
The wavelength multiplexer/demultiplexer 256 separates input optical signals into an upstream optical signal and a downstream optical signal according to their wavelengths. The wavelength multiplexer/demultiplexer 256 outputs an upstream optical signal input from the wavelength multiplexer/demultiplexer 249 to the wavelength multiplexer/demultiplexer 257 via a transmission line 588. The wavelength multiplexer/demultiplexer 256 outputs a downstream optical signal that has been input from the wavelength multiplexer/demultiplexer 257 via a transmission line 589 to the wavelength multiplexer/demultiplexer 249.
The wavelength multiplexer/demultiplexer 257 separates optical signals into an upstream optical signal and a downstream optical signal according to their wavelengths. The wavelength multiplexer/demultiplexer 257 outputs an upstream optical signal, which has been input from the wavelength multiplexer/demultiplexer 256 via the transmission line 588, to a transmission line 504. The wavelength multiplexer/demultiplexer 257 inputs a downstream optical signal, which has been received from another link end via the transmission line 504, to the wavelength multiplexer/demultiplexer 256 via the transmission line 589.
The power splitter 258 splits off an upstream optical signal transmitted through the transmission line 588 and inputs the split upstream optical signal to a port of the optical switch 210 via a transmission line 586. The power splitter 259 splits off a downstream optical signal transmitted through the transmission line 589 and inputs the split downstream optical signal to a port of the optical switch 210 via a transmission line 587. The optical switch 210 outputs an optical signal input from a port connected to the transmission line 586 or the transmission line 587 to a port connected to a transmission line 560.
While the optical gateway 2011 illustrated in
Splitting portions 250a in the optical gateway 2013 may also be configured as illustrated in
The present embodiment enables control of subscriber terminals during communication. Hereinafter, differences from the above embodiments will be mainly described.
The monitoring control device 267 includes a wavelength-variable receiver 268 and a wavelength-variable transmitter 269. The monitoring control device 267 can receive an optical signal of an arbitrary wavelength by the wavelength-variable receiver 268 and can transmit an optical signal of an arbitrary wavelength by the wavelength-variable transmitter 269. The optical gateway 2015 also includes a control device 235. When a subscriber terminal 40 is connected, the optical gateway 2015 uses the control device 235 to perform connection processing (such as registration and wavelength assignment) for the subscriber terminal 40 and start normal communication as described above in the first embodiment.
Here, a state where a subscriber terminal 40-1 has been connected to a link end B will be considered. The subscriber terminal 40-1 cannot communicate with the control device 235 because the subscriber terminal 40-1 is performing normal communication. Thus, the monitoring control device 267 connected to the optical switch 211 which is a small optical switch, is provided to enable not only monitoring of the communication status of the subscriber terminal 40-1 but also issuance of instructions for various setting of the subscriber terminal 40-1 or the like. That is, an optical signal separated by each power splitter 251 is output to the optical switch 211 via a transmission line 555. The optical switch 211 outputs the received optical signal to the monitoring control device 267. The monitoring control device 267 performs monitoring using the optical signal that the wavelength-variable receiver 268 has received from the optical switch 211 and further receives a control signal superimposed on the received optical signal. The wavelength-variable transmitter 269 of the monitoring control device 267 transmits a control signal for the subscriber terminal 40 by an optical signal. The optical switch 211 outputs the signal received from the wavelength-variable transmitter 269 to a port corresponding to the wavelength. A power splitter 251 multiplexes the control signal that has been received from the optical switch 211 via a transmission line 556 with an optical signal transmitted through a transmission line 512. With this configuration, even when the subscriber terminal 40-1 is performing normal communication, a request for connection destination change or the like can be received from the subscriber terminal 40-1 and a control signal can be transmitted to perform wavelength switching or like of the subscriber terminal 40-1.
Control signals which are slower than main optical signals between subscriber terminals and can be superimposed on main signals are used for communication of control signals between the monitoring control device 267 and each subscriber terminal 40. For example, a technique such as AMCC can be used.
In the present embodiment, electrical processing is performed on an optical signal extracted from the optical switch. Hereinafter, differences from the above embodiments will be mainly described.
The electrical processing unit 600 converts an optical signal into an electrical signal and performs electrical processing on the electrical signal and then converts it back to an optical signal and outputs the optical signal. The electrical processing unit 600 includes an O/E conversion unit 610, a processing execution unit 620, and an E/O conversion unit 630. The O/E conversion unit 610 corresponds to the O/E conversion unit 85 of
In
The wavelength control unit 310 notifies the processing execution unit 620 of a determination condition for determining which signal is to be subjected to electrical processing and the type of electrical processing to be performed on the signal. The processing execution unit 620 stores information on the determination condition and the type of electrical processing of which the wavelength control unit 310 has notified.
For example, in step S5 of
The first transmission wavelength is a wavelength for routing an optical transmission signal, which is an optical signal addressed to the communication destination subscriber terminal 40 from the requesting subscriber terminal 40, to the electrical processing unit 600. The second transmission wavelength is a wavelength for routing the transmission signal, on which the electrical processing unit 600 has performed transmission signal electrical processing, to a port corresponding to the communication destination subscriber terminal 40. The first reception wavelength is a wavelength for routing a reception signal, which is an optical signal addressed to the requesting subscriber terminal 40 from the communication destination subscriber terminal 40, to the electrical processing unit 600. The second reception wavelength is a wavelength for routing the reception signal, on which the electrical processing unit 600 has performed reception signal electrical processing, to a port corresponding to the requesting subscriber terminal 40. The first transmission wavelength and the second transmission wavelength may be the same wavelength and the first reception wavelength and the second reception wavelength may be the same wavelength.
Upon determining that transmission signal electrical processing is to be performed, the wavelength control unit 310 sets information on a first transmission wavelength as a transmission wavelength in a wavelength instruction to be transmitted to the requesting subscriber terminal 40. Upon determining that reception signal electrical processing is to be performed, the wavelength control unit 310 sets, information on a second reception wavelength as a reception wavelength in a wavelength instruction to be transmitted to the requesting subscriber terminal 40.
Upon determining that transmission signal electrical processing is to be performed, the OPS 300 issues an instruction to use the second transmission wavelength as a reception wavelength for the communication destination subscriber terminal 40. Upon determining that reception signal electrical processing is to be performed, the OPS 300 issues an instruction to use the first transmission wavelength as a transmission wavelength for the communication destination subscriber terminal 40. For example, in an optical gateway control unit 301 that controls an optical gateway 200 in which the communication destination subscriber terminal 40 is accommodated, a wavelength control unit 310 instructs a control device 230 to transmit a wavelength instruction in which a reception wavelength and a transmission wavelength for the communication destination subscriber terminal 40 are set.
Further, upon determining that transmission signal electrical processing is to be performed, the wavelength control unit 310 generates first instruction information in which a determination condition for identifying a transmission signal addressed to the communication destination subscriber terminal 40 from the requesting subscriber terminal 40, the type of transmission signal electrical processing to be performed on the transmission signal, a first transmission wavelength, and a second transmission wavelength are associated. Upon determining that reception signal electrical processing is to be performed, the wavelength control unit 310 generates second instruction information in which a determination condition for identifying a reception signal addressed to the requesting subscriber terminal 40 from the communication destination subscriber terminal 40, the type of reception signal electrical processing to be performed on the reception signal, a first reception wavelength, and a second reception wavelength are associated. The wavelength control unit 310 transmits an electrical processing execution instruction, in which the generated first and second instruction information is set, to the electrical processing unit 600.
When transmission signal electrical processing is performed, the optical switch control unit 320 controls the optical switch 210 such that a transmission signal of a first transmission wavelength transmitted by the requesting subscriber terminal 40 is output to the electrical processing unit 600 and the transmission signal of a second transmission wavelength input from the electrical processing unit 600 is output to a transmission line 541 corresponding to the communication destination subscriber terminal 40. When reception signal electrical processing is performed, the optical switch control unit 320 controls the optical switch 210 such that a reception signal of a first transmission wavelength input from a transmission line 542 corresponding to the communication destination subscriber terminal 40 is output to the electrical processing unit 600 and the reception signal of a second transmission wavelength input from the electrical processing unit 600 is output to a transmission line 522 corresponding to the requesting subscriber terminal 40.
For example, it is assumed that transmission signal electrical processing and reception signal electrical processing are performed on optical signals between a subscriber terminal 40-2 and a communication destination subscriber terminal 40 of the link end C. A transmission signal of a first transmission wavelength transmitted by the subscriber terminal 40-2 is output to the electrical processing unit 600 via the optical switch 210. The O/E conversion unit 610 converts the transmission signal input from the optical switch 210 into an electrical signal. The processing execution unit 620 refers to predetermined information included in the transmission signal converted into the electrical signal, and upon determining that a determination condition included in first instruction information is satisfied, performs transmission signal electrical processing corresponding to the determination condition on the transmission signal. For example, the processing execution unit 620 performs error correction such as forward error correction (FEC). The E/O conversion unit 630 converts the transmission signal, which is an electrical signal on which the processing execution unit 620 has performed error correction, into an optical signal of a second transmission wavelength indicated by the first instruction information, and outputs the optical signal to the optical switch 210. The optical switch 210 outputs a transmission signal of the second transmission wavelength to a transmission line 541 corresponding to the link end C. Performing error correction improves transmission characteristics.
The optical switch 210 outputs a reception signal of a first reception wavelength input from a transmission line 542 corresponding to the communication destination subscriber terminal 40 of the link end C to the electrical processing unit 600. The O/E conversion unit 610 converts the reception signal input from the optical switch 210 into an electrical signal. The processing execution unit 620 refers to predetermined information included in the transmission signal converted into an electrical signal, and upon determining that a determination condition included in second instruction information is satisfied, performs reception signal electrical processing corresponding to the determination condition on the reception signal. The E/O conversion unit 630 converts the reception signal, which is an electrical signal on which the processing execution unit 620 has performed reception signal electrical processing, into an optical signal of a second reception wavelength indicated by the second instruction information, and outputs the optical signal to the optical switch 210. The optical switch 210 outputs the transmission signal of the second reception wavelength to a transmission line 522 corresponding to the subscriber terminal 40-2.
An upstream optical signal of a subscriber terminal 40-3 and an upstream optical signal of a subscriber terminal 40-M are connected to the electrical processing unit 600 via the optical switch 210. The OLT function is implemented in the electrical processing unit 600. The processing execution unit 620 of the electrical processing unit 600 performs processing of the OLT function at an electrical stage. A plurality of subscriber terminals 40 are connected to the OLT. The processing execution unit 620, in which the OLT function is implemented, collectively manages the subscriber terminals 40.
The O/E conversion unit 610-1 converts an upstream optical signal of the subscriber terminal 40-3 input from the optical switch 210 into an electrical signal and outputs it to the processing execution unit 620. The O/E conversion unit 610-2 converts an upstream optical signal of the subscriber terminal 40-M input from the optical switch 210 into an electrical signal and outputs it to the processing execution unit 620. The processing execution unit 620 combines upstream electrical signals transmitted from the subscriber terminal 40-3 and the subscriber terminal 40-M into one signal and outputs the combined signal to the E/O conversion unit 630. The E/O conversion unit 630 converts the upstream electrical signal output by the processing execution unit 620 into an optical signal according to a wavelength instructed by the control device 230 and outputs the optical signal to the optical switch 210. The optical switch 210 outputs the upstream optical signal input from the electrical processing unit 600 to a transmission line 541 corresponding to the link end C. In this way, the electrical processing unit 600 receives a plurality of optical signals dropped by the optical gateway 2016, converts them into electrical signals, and multiplexes signals whose target link ends are the same by a multiplexing circuit, and then converts the multiplexed signal back to an optical signal and transmits the optical signal to the optical gateway 2016. This can increase the transmission speed. Although
The power splitters 507 between the subscriber terminals 40 and the optical gateway 2016 may each be a wavelength multiplexer/demultiplexer. For example, when the optical access system 116 is a WDM-PON, wavelength demultiplexers are used between the subscriber terminals 40 and the optical gateway 2016.
In the present embodiment, optical switches of different link ends are connected in a ring configuration. Hereinafter, differences from the above embodiments will be mainly described.
The optical switches or the optical gateways of the above embodiments are used as the optical switches 212. For example, it is assumed that the link end B in
Therefore, a connection from the optical switch 212a of the link end A to the optical switch 212b of the link end B via the optical switch 212c of the link end C by a clockwise path can be made using a counterclockwise connection from the optical switch 212a of the link end A to the optical switch 212b of the link end B as a backup, and the same connection in the opposite direction is also possible. Similarly, a connection from the optical switch 212-a of the link end A to the optical switch 212c of the link end C via the optical switch 212b of the link end B by a counterclockwise path can be made using a clockwise connection from the optical switch 212a of the link end A to the optical switch 212c of the link end C as a backup, and the same connection in the opposite direction is also possible.
Further, a counterclockwise path passing through the path P31, the optical switch 212b of the link end B, the path P32, the optical switch 212c of the link end C, and the path P33 or alternatively a counterclockwise path passing through the path P33, the optical switch 212c of the link end C, the path P32, the optical switch 212b of the link end B, and the path P31 can also be used as a backup for a connection between subscriber terminals 40a connected to the optical switch 212a of the link end A.
For example, in
An optical access system of the present embodiment has a function of stopping connections from subscriber terminals to an optical gateway. The optical access system realizes this function by providing, between each subscriber terminal and an optical switch included in the optical gateway, a shutter unit that performs switching between inputting and blocking an optical signal transmitted from the subscriber terminal to the optical switch. This allows the optical gateway to receive optical signals from subscriber terminals which are authorized for communication and not to receive optical signals from subscriber terminals which are not authorized for communication.
The control unit 302 is the control unit 20 or the OSP 300 in the above embodiments. The control unit 302 includes a wavelength management control unit 335 and an optical switch control unit 336. When the control unit 302 is the control unit 20 in the above embodiments, the wavelength management control unit 335 is the wavelength management control unit 25 in the above embodiments and the optical switch control unit 336 is the optical switch control unit 26 in the above embodiments. When the control unit 302 is the OSP 300 in the above embodiments, the wavelength management control unit 335 is the wavelength control unit 310 and the control device 230 or the control device 235 in the above embodiments and the optical switch control unit 336 is the optical switch control unit 320 in the above embodiments.
Each optical switch of the above embodiments can be used as the optical switch 213. The optical switch 213 has ports 11-1-1 to 11-1-P (where P is an integer of 2 or more) and ports 11-2-1 to 11-2-Q (where Q is an integer of 2 or more). Each port 11-1-p is connected to a subscriber terminal 40 via a transmission line 50-1-p (where p is an integer of 1 or more and P or less). The subscriber terminal 40 connected to the port 11-1-p will be referred to as a subscriber terminal 40-p. The port 11-2-1 is connected to the wavelength management control unit 335. The ports 11-2-2, 11-2-3, 11-2-4, 11-2-5, . . . are connected to the WDM device 80 via transmission lines. The WDM device 80 multiplexes optical signals of different wavelengths, which the optical switch 213 outputs from the ports 11-2-2, 11-2-3, 11-2-4, 11-2-5, . . . , and outputs the multiplexed optical signal to a multiplexed communication transmission line 90. The WDM device 80 also wavelength-demultiplexer an optical signal received via the multiplexed communication transmission line 90 and inputs the demultiplexed optical signals into the ports 11-2-2, 11-2-3, 11-2-4, 11-2-5, . . . of the optical switch 213. The optical gateway 2018 may not include the WDM device 80 while the ports 11-2-2, 11-2-3, 11-2-4, 11-2-5, . . . of the optical switch 213 are connected to subscriber terminals 40 or an upper level network via transmission lines 50-2.
The function of passing and blocking optical signals in the optical gateway 2018 will be described with reference to
The shutter 591 is an example of a shutter unit that performs switching between inputting and blocking an optical signal transmitted from the subscriber terminal 40 to the optical switch 213. Any device can be used as the shutter 591 as long as it can physically pass or block light. For example, an optical shutter such as a wavelength-variable filter or a wavelength-variable optical attenuator can be used as the shutter 591. The optical switch 13 can receive only optical signals from authorized subscriber terminals 40 by controlling the state of each shutter 591 such that it is set to a passing or blocking state. This prevents optical signals from malicious users.
A case where a new subscriber terminal 40 is connected to the optical gateway 2018 will be considered here. A new subscriber terminal 40 is first connected to the wavelength management control unit 335 and the wavelength management control unit 335 performs, for example, assignment of a wavelength to be used for communication with a communication destination to the new subscriber terminal 40. Therefore, the port 11-2-1 connected to the wavelength management control unit 335 is set as the connection destination of ports 11-1 to which no subscriber terminals 40 are connected.
When the new subscriber terminal 40 is connected to a port 11-1 of the optical switch 213, the new subscriber terminal 40 outputs a connection request optical signal to request new registration from the optical gateway 2018. Here, if a plurality of subscriber terminals 40 simultaneously output connection request optical signals of the same wavelength, a signal collision occurs in the wavelength management control unit 335.
In
On the other hand, it is assumed that a new subscriber terminal 40-2 is connected to the port 11-1-2 of the optical switch 213 via the transmission line 50-1-2 and a new subscriber terminal 40-3 is connected to the port 11-1-3 of the optical switch 213 via the transmission line 50-1-3. The subscriber terminal 40-2 and the subscriber terminal 40-3 transmit optical signals of the wavelength for requesting new registration. The connection destinations of the ports 11-1-2 and 11-1-3 are the port 11-2-1 which is an initial value of the connection destination. If the subscriber terminal 40-2 and the subscriber terminal 40-3 simultaneously output connection request optical signals of the wavelength i, a signal collision occurs in the wavelength management control unit 335.
The occurrence of this signal collision leads to failure of the registration of the new subscriber terminals 40-2 and 40-3.
Therefore, the states of the shutters 591 installed between the subscriber terminals 40 and the optical switch in the optical gateway 2018 are controlled such that a signal of only one of the subscriber terminals 40 that is newly registered in the control unit 302 is connected to the wavelength management control unit 335 via the optical switch 213. For example, the shutter 591-2 is set to a state of passing optical signals and the shutter 591-3 is set to a state of blocking optical signals. Then, after the subscriber terminal 40-2 switches to a wavelength assigned by the wavelength management control unit 335, the shutter 591-3 is set to a state of passing optical signals. By doing so, it is possible to avoid collision of optical signals in the wavelength management control unit 335.
The connection destination of each port 11-1 of the optical switch 213 is the wavelength management control unit 335 in an initial state as described above. Therefore, if a malicious user connects to a port 11-1 in an initial state, the wavelength management control unit 335 may be attacked. Thus, the states of the shutters 591 are controlled such that the ports 11-1 in an initial state of the optical switch 213 are prevented from receiving optical signals from unauthorized subscriber terminals 40. For example, shutters 591 corresponding to registered subscriber terminals 40 and a shutter 591 corresponding to a newly registered subscriber terminal 40 are set to a passing state and other shutters 591 are set to a blocking state. Then, the optical switch 213 performs control such that an optical signal of the newly registered subscriber terminal 40 is input from the port 11-1 in an initial state and the input optical signal is output to the wavelength management control unit 335 from the port 11-2-1. By doing so, it is possible to prevent optical signals from malicious users.
In order to perform the above control, the control unit may be provided with a shutter control unit that controls each shutter as illustrated in
The shutter control unit 337 shares various information such as subscriber information with other control functional units in the control unit 303. When a new subscriber terminal 40-p is connected, the shutter control unit 337 performs control such that a shutter 591-p corresponding to the subscriber terminal 40-p is switched from a blocking state to a passing state, based on subscriber information or the like registered in the control unit 303. Thus, when a new subscriber terminal 40 is connected, the shutter control unit 337 performs control such that shutters 591 corresponding to registered subscriber terminals 40 and a shutter 591 corresponding to the new subscriber terminal 40 are set to a passing state and other shutters 591 are set to a blocking state.
When a plurality of subscriber terminals 40 are newly connected to the optical gateway 2019 at the same time, the shutter control unit 337 determines the order of the subscriber terminals 40 according to the priorities of the subscriber terminals 40, the distances from the subscriber terminals 40 to the optical gateway 2019, or the like. For example, if logical conditions such as the priorities are the same, the shutter control unit 337 determines the order based on physical conditions such as the distances. The shutter control unit 337 performs control such that the state of a shutter 591 corresponding to each of the subscriber terminals 40 is switched from a blocking state to a passing state in a certain period of time according to the determined order. A subscriber terminal 40 newly connected to the optical gateway 2019 repeatedly outputs a connection request optical signal at regular intervals. Thus, a connection request optical signal transmitted at the timing while the shutter 591 is switched to a passing state is output to the wavelength management control unit 335.
Even when the wavelength management control unit 335 has a wavelength-variable selective reception function, a signal collision occurs in the wavelength management control unit 335 if the wavelengths of optical signals output from a plurality of subscriber terminals 40 newly connected to the optical switch 213 are the same. Thus, the shutters 591 are required.
A light detection function may also be implemented in each shutter 591. For example, each shutter 591 is provided with a photodetector that detects light. The shutter 591 detects an optical signal from a subscriber terminal 40 newly connected to a transmission line 50-1 by the optical detection function and notifies the control unit 302 of the detected optical signal. The shutter 591 may notify the control unit 302 upon detecting light having a predetermined intensity or higher or may notify the control unit 302 of information on the intensity of received light. The optical switch control unit 336 of the control unit 302 controls the optical switch 213 such that the subscriber terminal 40 corresponding to the shutter 591 and the wavelength management control unit 335 are connected and performs an initial connection operation. Alternatively, upon determining that the photodetector of the shutter 591 has detected signal light that is too strong, the shutter control unit 337 sets the shutter 591 to a blocking state such that the optical signal can be blocked as an abnormal signal. The signal light that is too strong is light of a level that damages components such as the optical switch 213 or causes signal deterioration due to nonlinear optical effects.
In addition, when a connection from a new subscriber terminal 40 has been detected even though its registration information such as subscriber information has not been registered in the control unit 302, that is, even though there is no plan for the connection to the optical gateway, the shutter control unit 337 determines that the connection has been made by a malicious user and can take a measure such as closing the shutter 591. For example, information on a subscriber terminal 40 to be newly connected is registered in the control unit 302 in advance. This information includes information on a port 11-1 corresponding to the subscriber terminal 40 to be newly connected and information on a period during which it is newly connected. Upon detecting an optical signal, the photodetector of the shutter 591-p notifies the control unit 302 of the detection. The shutter control unit 337 identifies a port 11-1-p corresponding to the shutter 591-p which has transmitted the notification. If there is no registration information of the subscriber terminal 40 newly connected to the port 11-1-p at the time when the notification is received, the shutter control unit 337 determines that the connection is made by a malicious user. In this case, the shutter control unit 337 sets the shutter 591-p which has transmitted the notification to a blocking state.
The optical signal can also be blocked when the port 11-1 of the optical switch is in an open state where the port 11-1 is not connected to anything, if possible in principle.
The optical gateways 2018 and 2019 may be provided with a shutter device 592 illustrated in
The shutter device 592 makes it possible to transmit or block optical signals of one or more desired wavelengths. The same number of shutters 594 as the number of wavelengths to be used need to be implemented in the shutter device 592.
A light detection function may be implemented in each shutter 594, similar to the above shutters 591. Upon detecting light, the shutter 594 notifies the control unit 302 or 303 of the light detection. The optical switch control unit 336 identifies a shutter device 592 in which the shutter 594-f which has transmitted the notification is implemented and a wavelength λf corresponding to the shutter 594-f which has transmitted the communication. The wavelength management control unit 335 determines whether the subscriber terminal 40 connected to the identified shutter device 592 is authorized to transmit an optical signal of the identified wavelength λf. Thus, if a subscriber terminal 40 outputs an optical signal of a wrong wavelength, the wavelength management control unit 335 can detect the signal. The wavelength management control unit 335 can also transmit a signal for wavelength setting again to the subscriber terminal 40, which has output the optical signal of the wrong wavelength, to allow it to reset the wavelength.
On the other hand, the shutter device 592 is also effective when the subscriber terminal 40 uses a plurality of wavelengths. For example, when the subscriber terminal 40 uses the wavelengths λ1 and λ2, the corresponding shutters 594-1 and 594-2 are opened and the other shutters 594-3 to 594-F are closed. This makes it possible to limit wavelengths that can be used by the user while preventing the inflow of signals of the other wavelengths. When the subscriber terminal 40 has started using a new wavelength, for example, the wavelength λ3, the corresponding shutter 594-3 is opened. This allows the subscriber terminal 40 to start using an optical signal (an optical service) that uses the new wavelength.
The optical gateways 2018 and 2019 may also be provided with a shutter device 596 illustrated in
The optical access system 118 illustrated in
In
As described above, of shutters 591 corresponding to subscriber terminals 40 communicating with the same communication destination, a shutter 591 corresponding to a subscriber terminal 40 which is at the time of communication is set to a passing state and shutters 591 corresponding to subscriber terminals 40 which are not at the time of communication are set to a blocking state. Thus, subscriber terminals 40 which are not at the time of communication are physically unable to communicate. In the case of the optical access system 119, the shutter control unit 337 switches the blocking and passing states of each shutter 591. When the gateway 2018 includes the shutter device 592 instead of the shutter 591, the subscriber terminal 40 switches the states of blocking and passing an optical signal of a wavelength to be used to communicate with the same communication destination as that of other subscriber terminals 40. In this way, the times at which shutter units corresponding to a plurality of subscriber terminals 40 having the same communication destination transmit and input optical signals transmitted from the subscriber terminals 40 to the optical switch 213 are displaced such that the times do not overlap. This prevents signal collisions between the subscriber terminals 40.
In the present embodiment, it has been described that the shutters are arranged in the optical gateway as an example of the arrangement location of shutters, but the shutters may be installed outside the optical gateway (for example, between the subscriber terminals and the optical gateway). Alternatively, the shutters may be arranged in the subscriber terminals.
In the present embodiment, the optical access system may be configured to allow the optical switch to be controlled such that optical signals to be blocked are output to a termination device that terminates the optical signals as illustrated in
When subscriber terminals 40-2 and 40-3 are not authorized to communicate, the optical switch control unit 336 controls the optical switch 2020 such that an optical signal input from the port 11-1-2 is output to the port 11-2-(Q — 1) and an optical signal input from the port 11-1-3 is output to the port 1-2-Q. Thus, the optical gateway 2020 blocks optical signals received from the subscriber terminals 40-2 and 40-3 such that the optical signals do not affect communication of the other subscriber terminals 40.
Photodetectors having an optical detection function may be implemented in the ports 11-1 on the subscriber terminal side of the optical switch 213 or may be implemented between the subscriber terminals 40 and the optical switch 213. Upon detecting light, each photodetector notifies the control unit 302 of the detection. The optical switch control unit 336 identifies a port 11-1 where the photodetector which has transmitted the notification is implemented or connected. Upon determining that the identified port 11-1 is not a port 11-1 connected to a subscriber terminal 40 which is authorized to communicate, the optical switch control unit 336 controls the optical switch 213 such that a signal input from the identified port 11-1 is output to a port 11-2 connected to the non-reflective termination device 599.
Superimposition of an AMCC signal on a main signal will be described. In the optical domain, the same wavelength is used for an AMCC signal and a main signal. A main signal is a signal such as that of a common public radio interface (CPRI) such as an on-off keying (OOK) signal of 10 Gb/s (Gigabits per second). An AMCC signal is transmitted, for example, by superimposing a 1 MHz carrier wave on a main signal and conveys information by intensity modulation. Such a low-speed AMCC signal is superimposed on a main signal and the AMCC signal thus superimposed can be separated from the main signal.
In the electrical domain, different frequencies are used for an AMCC signal and a main signal. An AMCC signal has a narrower band than a main signal. For example, a power multiplexer combines a 10 GHz electrical main signal and a 1 MHz electrical AMCC signal and a transmitter converts the combined signal into an optical signal to generate a main signal on which the AMCC signal is superimposed. Another frequency such as 500 kHz that does not overlap with the electrical main signal may be used as the carrier frequency and another modulation method such as phase modulation may be used as the modulation method.
The control devices 230 and 235, the monitoring devices 260 and 265, the monitoring control device 267, the wavelength control unit 310, and the optical switch control unit 320 described above may include a central processing unit (CPU), a memory, an auxiliary storage device, and the like that are connected by a bus and realize some or all of the above functions by executing programs. Some or all of the functions of the control devices 230 and 235, the monitoring devices 260 and 265, the monitoring control device 267, the wavelength control unit 310, and the optical switch control unit 320 may also be realized using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA). The programs for the control devices 230 and 235, the monitoring devices 260 and 265, the monitoring control device 267, the wavelength control unit 310, and the optical switch control unit 320 may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a portable medium such as a magneto-optical disc, a ROM, or a CD-ROM or a storage device such as a hard disk built in a computer system. The programs may be transmitted over a telecommunication line.
The wavelength control unit 310 and the optical switch control unit 320 may be implemented using one information processing device or may be implemented using a plurality of information processing devices that are communicatively connected via a network.
According to the above embodiments, an optical communication apparatus includes an optical switch, a wavelength management control unit, and an optical switch control unit. The optical switch is connected to a plurality of transmission lines and outputs an optical signal input from one of the transmission lines to another of the transmission lines. The wavelength management control unit assigns a wavelength to a subscriber terminal according to a communication destination. The optical switch control unit controls the optical switch such that it outputs an optical signal transmitted from the subscriber terminal, to which a wavelength has been assigned, to a transmission line corresponding to its forwarding destination on a path from the subscriber terminal to the communication destination. In this way, the optical switch distributes the output destinations of optical signals according to the paths. The communication destination is, for example, another subscriber terminal that opposes the subscriber terminal to which the wavelength has been assigned. The forwarding destination is each of various devices or various functional units on the path from the subscriber terminal to the opposing subscriber terminal, such as the opposing subscriber terminal, a control unit, an electrical signal processing unit, or a power splitter (for example, a coupler).
The optical switch control unit controls the optical switch such that an optical signal input from a transmission line is output to a transmission line corresponding to a forwarding destination identified by a combination of a subscriber terminal that has transmitted the optical signal and the wavelength of the optical signal. Alternatively, the optical switch control unit controls the optical switch such that the optical signal is output to a port connected to a transmission line corresponding to a forwarding destination identified by a combination of the subscriber terminal that has transmitted the optical signal, the wavelength of the input optical signal, and a port from which the optical signal has been input. Alternatively, the optical switch control unit controls the optical switch such that the optical signal is output to a port connected to a transmission line corresponding to a forwarding destination identified by the input port alone, by the input port and the subscriber terminal, or by a combination of the input port and the wavelength if the wavelength and the subscriber terminal have a unique relationship in the optical switch.
According to the above embodiments, a setting that allows the use of a path corresponding to a destination can be made on a transceiver of a subscriber terminal and a signal transmitted from the subscriber terminal can be relayed according to the destination using the path. Further, after initial setting of the subscriber terminal, it is possible to relay the optical signal according to the destination while reducing delay as compared with the related art.
Although embodiments of the present invention have been described above in detail with reference to the drawings, the specific configurations thereof are not limited to those of the embodiments and also include designs or the like without departing from the spirit of the present invention.
1 Optical communication system,
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/051305 | Dec 2019 | JP | national |
| PCT/JP2020/005782 | Feb 2020 | JP | national |
| PCT/JP2020/033760 | Sep 2020 | JP | national |
The present application claims priority to PCT/JP2019/051305 filed on Dec. 26, 2019, PCT/JP2020/005782 filed on Feb. 14, 2020, and PCT/JP2020/033760 filed on Sep. 7, 2020, the contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/036878 | 9/29/2020 | WO |
